I'm kinda new to the plannar/magnepan world, but I am really interested in trying out a pair after all the reviews I've been reading. From what I understand these speakers are quite power hungry. What is the minimum I need to properly drive these? 
I currently have a VAC Avatar integrated tube amp. These are the stats:
Type: Integrated vacuum tube amplifier with MM phono stage and home theater (direct power amplifier) mode.
Tube Complement: two 12AX7 low noise (phono), two 12AX7 (line stage), three 12AU7/6189A (power amplifier), and four EL34 (power amplifier)
Options: Remote control for volume (motorized direct control) & mute
Power amplifier ("Home Theater" direct mode):
Output matching: 4 or 8 ohms nominal
Power output: 60 watts/channel ultra-linear; 27 watts/channel triode
Frequency response: 9 Hz - 35 kHz +0 / -0.5 dB, 3 Hz - 71 kHz +0 / -3.0 dB
Power bandwidth: 11 Hz - 63 kHz + 0 / -3.0 db ref. 50 watts
Gain: 25 dB ultra-linear; 23 dB triode
Residual noise: 1.5 mv at 8 ohm output
Channel separation: -72 dB @ 1 kHz; -60 dB @ 10 kHz
Line stage preamplifier:
Gain: 24 dB
Maximum input signal: Infinite (attenuation precedes line stage)
Noise contribution: Approx. 0.1 mv at power amplifier output 
THD contribution: Approx. 0.04% 
Tape output: Unity gain from selector, non-inverting 
Phono stage preamplifier: 
Gain: 37 dB (measured at tape output)
MC phono stage in place of the MM optional 
Residual noise: 3 mv at output (S/N ratio approx. 69 dB) 
Overload: 117 mv @ 1 kHz = 8 volts RMS output, 460 mv @ 10 kHz 
Frequency response: RIAA +/- 0.25 dB 
Notes: Does not invert absolute phase. 

Anyone know if these will do or if I'll have to upgrade? Love the tube sound . . . will I need to go solid state for Maggies? Thanks for putting up with the noobie question :) 
I think the best person to answer this is Ralph (atmaspere).
Though if I remember correctly, some of the Maggies operate at low impedances which might tax a tube amp. In which case, you could get one of the Zero transformers.
I am new to tubes, so I may be wrong.
it isn't power per se so much as power into a lower impedance - there are impedance curves online for at least some models

IIRC, they get to about 4 ohms at higher freq.s

I use a Sunfire Cinema Grand biamping 1.5 QRs in a big room with no problems at all

BTW, easier load to drive than most electrostatics
100 watts per side of tube amp power will drive most maggies. I have 3.6's and have driven them with as little as 40 watts per side. I now biamp my 3.6's and have about 200 watts per side. In my opinion Maggies sound best with tubes.
Though I am a Vandersteen fanboy, I do like the sound of Maggies.
+1 Ahendler, I too think 100 watts should be sufficient.
Here is a link to Atma-sphere and his endorsement for the Zero:
- it is on the right side of the page about mid-way down.
Much depends on what SPLs you enjoy. Your VAC will certainly drive Maggies, but- whether it will run out of steam, before reaching your preferred level, is another matter. An in-home audition is the only way to know for certain. Toting your VAC to a Magnepan dealer for an audition, will give you a good idea also. Then again, Magnepan offers in- home auditions on a couple models. They were actually paying people to try the 1.7i, in home and the MMg has a 60 day return policy:  btw: The size of your room and distance between the listening seat and speakers are also considerations, when discussing power requirement.
My VAC 30/30 was able to drive my Martin Logan SL-3's and Magnepan 1.6's and 1.7's at normal volumes in a medium size room. Your Avatar should have no problem. That said, I would highly recommend you listen to them first. I didn't care for either pair.
I have Magnepan 1.7s in a medium-sized room (about 350 sq ft).  I originally used a Linn Majik amp with 100 wpc @4 ohms.  The sound was plenty loud enough, but it just did not have enough dynamic punch.  I then changed to a Linn Klimax amp with 200 wpc @4ohms and got the dynamic punch that I was looking for.  In my view, 200 wpc is much better than 100 wpc.  I am very happy with 200 wpc and have not plans to add more power.
Nature Boy,

     I agree with gdnrbob, that Ralph (atmasphere) is probably the most knowledgeable about driving Magnepans with tube amps.  I know Maggies are all a relatively stable load of 4 ohms, only dipping slightly below this at certain frequencies. There are no crazy impedance dips like some electrostatics.  I also know there are many Maggie owners who drive  them with tube amps, although I think most use more than 40 watts.

     I own an older pair of 2.7QR Magnepans and have always driven them with high powered solid state amps,  my experience being the more power the better they performed.   initially I used a 400 watt class A/B amp and currently use 1,200 watt class D monoblcks.  The bass and dynamic range of my spkrs improved with the addition of more power.

    Another solution you may want to consider is pairing a good tube preamp with a solid state amp.  If you take this route, however, it's important you match the preamp's output impedance to the amp's input impedance, the general rule being the amp's input impedance should be at least 10 times the preamp's output impedance for best performance.  If you decide to use a class D amp, however, it's also very important you match the sound of the preamp to your personal sound preference since good class D amps are very neutral and your system' sound will be mainly dictated by the sound of your preamp and sources.

     Several Audiogon members have mentioned that Magnepan does not recommend using class D amps with their spkers.  This makes absolutely no sense to me because I have found them to be ideal for driving my panels. Class D amps are relatively inexpensive, very transparent, small, efficient, run cool and usually have plenty of power.  If you don't find a suitable tube amp at an affordable price, you might want to consider finding a tube preamp you like and match it to a good class D amp.  This hybrid approach will likely give you a tube sound without so many tubes to maintain and at a reduced cost.

Hope this helped a bit,
I have two sets of Maggies, 2.5Rs, and 3.6Rs.  (I love em, I also have electrostatics(ML) and time aligned cone speakers (Vons), but the maggies rule.) I can run the 2.5s with a 40 watt all tube integrated, and they sound great, but that same amp just can't push the 3.6s hard enough (for me anyway). However, that said, I do run the 3.6Rs with a 50 watt (rated 50 - but closer to 70 - per the owners manual. yeah really) tube power amp (Cary V12R).  This amp has the 3.6s singing like angels (I'm guessing angels can sing really good?).  I have several solid state amps also, but the Cary with the Maggies seems to be a match made in heaven.

     In my last post I mentioned that I'd heard it mentioned that Magnepan does not reccommend using class D amps to drive their speakers.  I went to their website and found out this is not totally accurate:

     They recommend class A/B amps that are high current designs (amps that double their 8 ohm wattage into a 4 ohm load, example: 100 watts @ 8 ohms and 200 watts @ 4 ohms).  They tout this type because they claim it has worked well on Maggies for decades according to feedback from their customers.

     They state that they don't recommend class D amps because they have received reports of some shutting down when driving their 4 ohm speakers.  They further state they don't have the time or staff to keep track of which class D amps work well and which do not so therefore, in a self described effort to be conservative,  decided to just not recommend any of them.  Stating that you decline to make distinctions between amps of a specific type is not exactly a ringing endorsement but it is obviously does not rule out that some class D amps may be ideal matches for their speakers.

     The truth is that Magnepan does not recommend or state not to use class D amps, it merely states  it can't be bothered with details like which amps work well and which do not  and, besides, we already told you we  don't want to be bothered.

     Magnepan apparently can't be bothered with the fact that there are numerous class D amps that are high current and double their power from 8 to 4 ohms.  Mine are rated at 600 watts @  8 ohms and 1,200 watts @ 4 ohms and, whether Magnepan gives a hoot or not, drive their speakers very well..

A lot of great info here. Thanks so much! Quite a bit to consider with this next purchase(s). 
Heard something about SERVO amps being a good option? Not necessarily going that route, but as long as I'm considering switching out my current integrated amp I might as well put it out there. 
Tim, thanks for all the info and the mention of class D. I will look into that as well.
Larry, the maggies I'm looking at happen to be 2.5's so might not have to get rid of my VAC? 
I've never tried tube amps with my Magnepans but will say that you need a lot of solid-state power, if you're going to listen above 70db.  I'd recommend something like the Sanders Magtech, which does 900 into 4 ohms.
they choose amps for use at shows and demos

I think they used Bryston to demo their bass panels
The other key piece of info, I suppose, is the listening area. I'm setting them up in my living room, so it's an open space with furniture (and wooden floors) I'm working with. Not sure if this automatically means more power needs  . . . the immediate listening area is about 250 square feet, but the whole room is about 650 sqft 
As far as Class D, I did directly compare the Spectron Musician III Mk.2 with all upgrades to the Sanders and found that it sounded fairly similar. The Spectron may have edged out the Sanders when connected with balanced connections, but I just couldn’t pull the trigger because of some strange interference issues that I couldn’t eliminate.  The Sanders seemed a little more natural, and the Spectron seemed a little better in vocals. 

However, assuming that both amps function fine, I’d probably recommend the Spectron just because it’s usually cheaper than the Magtech on the used market by $500+.
Wyred SX 1000r mono's sound great on Maggie. 1200 wpc into 4 ohm, 2000 damp factor. Full meaty sound with great stage.

     I don't want to talk you out of using tube power on the 2.5 Maggies, they have a ribbon tweeter that I would imagine sounds great driven by tubes.  The VAC Avatar is a very good tube integrated but the truth is that 60 watts may not give you enough juice to properly drive the inefficient (84 db) 2.5s, especially the woofer section.

      It may work okay if you don't play your music too loudly and your room isn't too big.  If you listen to music with strong bass, or listen at high volumes or your room is large, I think you may be happier with a powerful (300+ watts at 4 ohm) ss amp.  When I moved from 400 watts of class A/B power to 1,200 watts of class D power, the biggest benefits were the Maggies sounded much more dynamic and the bass was the best I'd ever heard on my panels.   Class D amps typically have very high Damping factors which means woofer cones and panels are very well controlled  on both starts and stops.  This results in very solid, taut and tuneful bass. If good bass is important to you, you will definitely attain better bass performance with a class D amp than either the VAC or a class A/B and the more watts the better.

Good luck,


or use a transistor amp (MOSFETS anyone) in a topology that sounds tubey

add a real tubey pre-amp
I can second (third) the Wyred for Sound amps. I have a Wyred STE500 (550 w/ch into 4 ohms) and am quite pleased. It is paired with Maggie .7's which are wonderful for their modest price. Current is the key with Maggies. I was driving them with a Rogue Sphinx which sounded quite good too. The Wyred amp really brought them to a different level. I will say I added a sub to fill out the bottom which was a fine addition, it is a Speedwoofer and pairs fine with the Maggies.

"or use a transistor amp (MOSFETS anyone) in a topology that sounds tubey

add a real tubey preamp"

The better class D amps usually do use MOSFETS due to their high quality sound and ability to turn on/off very quickly. MOSFETS are excellent output devices/transistors that sound great and are typically used  in the better class A  and class D amps. 

If natureboy wants a real tubey sound, pairing a real tubey preamp with a class D amp will deliver that sound because they are very neutral and will just faithfully ampify the output of the preamp without any alteration.  This is exactly why I recommended  this combo to him in my initial post.  A VAC preamp paired with a Wyred amp, or any similarly good class D amp, would likely be a very good solution.  


     I think a Vac pre-amp properly matched in impedance to a good class D amp and connected with quality XLR interconnects, would result in a sound very similar to your Avatar but with significantly more power.  Most good class D amps offer no risk in-home trial periods of up to 30 days.  If you're not satisfied, you can return it at no, or a minimal, charge.  

     If you decide on this route, I'm fairly certain you'll get plenty of good suggestions here on this thread concerning which amp  to match to your preamp choice if you request assistance. Again, my opinion is that a VAC preamp is a great choice but almost any preamp you choose can probably be matched to a good amp within your budget..

Thanks for all the great info, guys! A lot of really good options to think about. 
Anyone else hear about SERVO amps working well with these speakers? 
I've used multiple amps on Mag 3.7s over the last few years.....

The best amps are the ones I have now, Bryston 28BSST2
runner up, Bryston 7BSST2
after that in order of "best sound"
Pass X350.5
Zesto Eros (I have a semi large room, and even these class A beasts seemed to run out of gas with the 3.7s)
Manley Neos (By far the worst sounding amps I've ever heard.....I cannot BELIEVE any person with average ears would keep these)  also ran out of gas quickly....

I do not believe tubes in general are a good fit for the Magnepans.
I do love a tube pre with them though, I run Convergent SL1 Renaissance w/ Phono

Magnepan has presented at the shows for years w/ Bryston, and I do think they are the top of the mark in terms of synergy.....I have excellent bass control, decent low end, sparkling highs and a meaty musical involving presentation with this need a lot of juice with Magnepans to give them the headroom that you'll want.....

I've put some vids on utube, just search Magnepan Convergent
food for thought......I am pushing the 20.7's with the Devialet Expert Pro 1000's .  These are hybrid class A/D technology and I could not get Magnepan to provide an opinion.....but comparing to other amps i have owned IMO they sound the best they ever have......  using the Berkeley Ref DAC to that may be helping greatly.......


     I agree that the Bryston  28BSST2  mono-block amps would probably be the best sounding amps for Natureboy's 2.5 speakers.      
     The bad news is that a pair of these mono-blocs new were about $15,000  (Natureboy didn't state his budget but I assumed it wasn't unlimited), they're huge and weigh about 100 lbs/ each, are very inefficient and emit a tremendous amount of heat.

     Good class D mono amps (such as Wyred, Bel Canto or D-Sonic), in the opinion of 6Moons reviews, are about 90% as good at 1/4 the price or less. Plus they're small, weigh about 10 lbs/each, are very efficient and emit very little heat.  

     Natureboy will need to decide which factors are most important to him.



The best amps are the ones I have now, Bryston 28BSST2
runner up, Bryston 7BSST2
after that in order of "best sound"
Pass X350.5
Stewart, how would you describe the sonic difference between the 7BSST2 and the Pass 350.5? I am toying with the idea of  buying either the 7B3´s or a Pass 250/350.8 for my 3.7´s.
Alot of great info above , I sold maggies for yrs and ran many tubes and ss through them ( lots of free time at the ole’ brick and mortor ).I have also owned most of them over the yrs except tympanis ,that being said i ran cj personnally and biamped the low end with ss ( bryston, krell ,M.L , cj luxman etc ) am a big vac fan and believe it will drive them .It will run out of steam , but will be magic at med volumes if they are properly setup and the room is treated well . The phi 110 vac will bring more power . With planers power usually is your freind lots of it imo .Personally i always found tube top ss bottom was the juice for planers ..which you could do with your vac . Maggies sound best when they can breath,they can be very placement sensitive . i am in a med room now or i would have 3.6 maggies .. and here i go purist dont throw stones please : ) but i alway ran two fast powered subs also ..jazz rock etc ... jmho
good luck
Noble 100,   Actually, they are about 20K new

I'm not giving him the info to say go out and buy a 2KW pair of monoblocks......I am giving him the information to illustrate that in my experience and flea watt tube amp is not a great option.......I have never heard a Class D amp I liked, but others will have differing opinions, but between a top flight class D and a mid flight tube, I'd probably go Class D also......

The thing that struck me instantly on the Brystons was low level is miles better than the Pass X350 I had.....beyond that, they're both musical, but I'd give the edge to Bryston......with other speakers it could be a different matter, but on the 3.7s, I far prefer the Brystons.  I will say that I feel the 28s are not marginally better in terms of musicality versus the 7s.  If I was doing it again, I would probably stick with the 7s....
I have owned the Magnepan 1.7's for five years now.  Decided to upgrade my Cambridge integrated (which did not sound bad at all driving the 1.7s).  On paper I thought the VanAlistine fet valve 600 would be superb with its combination of a tubed input and tons of power (probably put out 500wpc into 4 ohms).  I listened for several weeks and the magic never happened.  All that power and I just wasn't taken--not even one  "wow".
This was a secondary system for me and I was ready to sell the maggies and simplify with a nice sacd/integrated and perhaps a pair of vsa vr-22's.
When the marantz gear came (8004 series) I hooked it up to the 1.7's and right out of the box I smiled.  Amazing.  An integrated rated at 70wpc creating all that beautiful music--so smooth and detailed and dimensional and dare I say even punch.  So the 1.7's  were staying.  I returned the 8004 series (at no loss) to my dealer and upgraded the Marantz Reference 15s2 series and never looked back.  This integrated is rated at meager 140 wpc into 4 ohms.  I listen to music at relatively loud/realistic volumes and have NEVER felt shorted.  (But you ought to see the power supply in the amp).  I can honestly say that while it's fun to look, I do not see myself ever moving on to "better" or more powerful electronics. (ok, maybe the marantz 11s3 series)  Hope these thoughts are useful.

     Thanks for your clarification.  I agree with everything you stated in your last post, especially that flea watt tube amps should be avoided.  But I don't think you or I consider the VAC Avatar to be a flea watt amp at 60 watts and with a solid power supply. 


     I think members could better assist you if you declared a budget for your potential new amplification purchase..  As you know, there are a wide range of amp options for driving Magnepans.  

    Through stewart's personal experience, he can attest that either the Bryston 28s or 7s will likely drive  your 2.5 speakers very well since they work so well on his 3.7s.  I have no reason to doubt that either amp would be a good choice for the 2.5s.

     Through my own and several other posters' personal experiences on this thread, we can attest that high powered class D amps (Wyred, Bel Canto and D-Sonic) will also likely drive your speakers well  since they drive our Magnepans so well.  I tend to think all these amps (including both Brystons) will drive the 2.5s well and that you will need to decide between them based on personal auditions and your budget.  

     What you don't know at this point, however, is how well your current VAC Avatar integrated will drive your Magnepan 2.5s.   I think the best approach would be to thoroughly test out your VAC on the 2.5s prior to considering any changes.  When I state 'thoroughly test out' I mean not only that it sounds good to you but also that it drives them effortlessly at your normal listening levels and that there is sufficient detail, 3-D sound staging and headroom in your opinion.  

     If you're not totally satisfied with the VAC's performance, then at least you have some very good suggestions for possible alternatives.


In the context of driving 91db efficient speakers, 60w is just fine, in the context of magnepans, whatever their efficiency, it is flea watt in my opinion in an average sized room....

To clarify, I mention my luck with amps in terms of brands only.....I would never recommend this op should buy a pair of 28bsst2s to drive 2.5s, or even 7s for that would be ludicrous to spend a lot of money on amps to drive 2.5s, when he could take a fraction of those dollars and upgrade to 3.7s or 1.7i etc etc.  No matter what amps he puts on these they will sound veiled as all maggies were in that era, all the way up to 3.6s......if he stays with 2.5s check the used ads and buy the best class d amp you can find......if it's integrated, all the better!  see what specials underwood hifi has going, he had some emerald physics amps not too long ago that looked really good for the money......
Just looked and my last sale email from underwood hifi showed he had emerald physics 100.2 amp for either 599ea @ 100w pc, or two for 999, for 250w in mono, 

That's about 70 percent off or so and they're new......Walter @ Underwood is a great guy......


     The Magnepan 2.5R are 84db (the 3.7 are 86db and the 2.7 are 87db)..  I would consider all of these as inefficient speakers but not sufficiently so to rule out the use of the 60 watt Vac Avatar as long as the room isn't too large and the volume ismoderate. The speaker's 4 ohm impedance may be a bigger issue, however, the VAC does have 4 ohm  speaker taps.  I don't think we know enough about natureboy's room, budget or listening habits to rule out the use of his VAC.

    I think your suggestion of the Emerald Physics 100.2, (currently on sale for $599) may be a good match for the 2.5s.  I own a 100.2SE(150 watts/ch @ 4 ohms)  and use it in bridged mode(450 watts@ 4 ohms) for my CC3 center channel.  When I first received it I tried it out in stereo mode on my 2.7s (just out of curiosity) and it drove them very well; very good bass,  very dynamic,dead quiet and finely detailed  with a very sweet and smooth mid-range and treble.  It uses an analog power supply(not a switch mode power supply) and the amp is stable down to 2 ohms.  Of the 3 brands of class D amps I own, I think the Emerald Physics has the most tube-like mid-range and treble while still possessing the typical class D excellent bass response. 

    While I think this amp in stereo would perform very well driving Natureboy's 2.5s with its 100 watts/ch, I think buying 2 and bridging both to mono for 250 watts/ch is likely to give natureboy the best performance from his 2.5s, well worth the added expense.  


So both the  3.7s and the 1.7i would be upgrades to the 2.5's I'm looking at? I'm not quite a Magie expert, so input like this is definitely very valuable. If I can get a better speaker for a reasonable increase in price I can definitely look into it. 

I can start out by testing them with the avatar and if they are falling short, then I would switch out components. Class D was something I had not considered, but you are definitely making a strong case for them. Specially if I can get a tubey sound by preamp. I didn't know preamp dictated the sound as much as it seems to; I always thought amps would color your listening experience more than a preamp. 
I am listening in a rather large sized room (IMO)  . . it's a living room area with wood floors and it's about 650 sqft more or less. Maybe closer to 700. I have a pretty varied musical taste (as many people here tend to have), I tend to listen to a mix of classic rock, prog, jazz and classical. 
ok, I use a Sunfire Cinema Grand amp to drive my 1.5QRs...

The $$ allocation should likely be better speakers, then better amp.  The 3.7's are acoustically smaller than the 1.7's so why not consider those? (That is fresh and straight from the horse's mouth - may even be on their web site).

I'd love to have Bryston's too but they are not cheap - maybe the Canad. dollar will fall to 1% of where it is now...

A Maggie dealer near me is using a Rogue for drive but it is still $4k.  I'd say go for the 3.7s first and may do the same myself.
Nature boy, go read Harry Pearson's review of the 3.7's in Harry's Workshop, absolute sound and jonathan valins follow up's a good explanation of why the .7 variants are such a huge upgrade over past Maggie iterations......quasi ribbons have a LOT to do with it, the .7i's are yet another step beyond......I think you would see a night and day difference, and with amps, probably not.......
1.7 is also > 2.5r or only the 1.7i that you mentioned? 

you're saying the 3.7 is better than the 1.7 or vise versa? 
Nature boy,

The 2.5r is a very old speaker.....the 1.7 would be quite a bit better, and the I a little better than that......of course the 3.7 or 3.7i would be an even more substantial bump in's really a function of room size, the 3.7 is just a larger speaker than a 1.7......

The thing that struck me instantly on the Brystons was low level is miles better than the Pass X350 I had.....beyond that, they're both musical, but I'd give the edge to Bryston......with other speakers it could be a different matter, but on the 3.7s, I far prefer the Brystons.  I will say that I feel the 28s are not marginally better in terms of musicality versus the 7s.  If I was doing it again, I would probably stick with the 7s....

stewart, did you find the X350.5´s bass boomy and ill defined compared to the 7B SST´s? Do you mean the difference between the 7´s and 28´s is only marginal?

while the the 3.7 is a physically larger speaker than a 1.7, Maggie themselves will tell you it is acoustically smaller

so will sound better in a smaller room

3x more spendy tho

When I say low level detail, I'm referring to minute details such as decay of a piano, or revealing of things you hear in older jazz recordings in a quiet passage such as a chair creaking, or the subtle brush of a those areas I thought the Bryston was better.  The X350 is certainly no slouch in the bass department......

The overall signature of sound for 7s versus 28s is so very similar, that if a person's wattage/headroom/room size needs were served by a pair of 7s, I would stick with it......I had a chance to get a pair of 28s for not a huge amount for upgrade, so I went for it......and while it's true it sounds like there is more headroom, the 7s still sounded similar for half the money.....but the 28s aren't leaving :)
I think my listening room is a bit on the large size, so guessing the 1.7's would be better suited? 
Setup is in my living room area which merges right into the dining room, so it's a good percentage of the whole house. The whole house is about 2100sqft, so I'm guessing living/dining area are about 700-850 sqft, roughly

Thanks stewart, was it the X350 or 350.5 you owned?

Based on what I´ve heard the .8-series should be more neutral vs the more lush sounding .5´s.

I think my listening room is a bit on the large size, so guessing the 1.7's would be better suited?

The 3.7 or 20.7 will work better in a large room. 

An oversimplification would be:
Small room - small speaker (.7 or 1.7)
medium sized room - medium sized speakers (1.7 or 3.7)
large room - large speakers (3.7 or 20.7)


    As stewart0722 mentioned, the 2.5/R are older speakers circa 1987.  They have a freq. range of 37-40,000 hz +/- 3 db.  A big plus of these spkrs is that they have the very good true ribbon tweeter panel section, not the QR (Quasi-ribbon)  tweeter panel section used in some other Maggies. 

     Here's my opinion of the sound quality performance heirarchy of Magnepan spkrs I think you're considering (from best to least in sound quality performance):

1. 3.7i  - Circa 2014,  $5,995/pr. 

2. 3.7/R -Circa 2011,  $5,495/pr.

3. 3.6/R -Circa 2000, $ used/pr.?

4. 2.5/R- Circa 1987 $ used/pr.?

5. 1.7i-  Circa 2014 $1,995/pr.

     These rankings are just my opinion and others may disagree.  I'm not going to go into great detail to explain my rankings or the differences between the models.

       I also want to add that I've auditioned all of these, with the only exceptions being the "i" versions,  at audio stores only  and not in my system/room.

      I ranked  the 1.7 and 3.7 "i" versions superior to the base models of each based on their overwhelmingly opinions of the "i" versions superiority by professional audio reviewers and my own opinion that Magnepan would not have added these versions unless they were convinced that  both were significant  improvements.  

     I believe the 2.5/R is likely the best value of the bunch since it has the excellent true ribbon tweeter section and would be the least expensive.  The  3.6, 3.7 and 3.7i, in my opinion,  are going to be clearly superior to the 2.5  but I believe the most noticeable difference will be the improvement in bass performance which is significantly more effective on the 3.6 and above.  Used or demo versions of 3.6/R and 3.7/R may also represent bargains. 

     If you have a local Magnepan dealer, you should visit and audition some of these for yourself.  The dealer may even allow you to home demo some.  

I did not read all the posts, so if this is a repeat, I'm sorry. 
The Avatar is a great amp, first of all. I love it, owned one. Second, Kevin Hayes, owner, designer of VAC, would be your best source of 'What if'.
He will be completely honest.
BTW, the Maggies, are an almost flat, IIRC 4 ohm load.
Also, someone mentioned the 60 Day Trial, I'd do that.
Good luck.