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 :) 

    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.

I have the Avatar you have, and I once had Magnepan Mg2a's.  First, old Maggie's can have a problem with the glue deteriorating, and it's not always obvious to the listener.  Second, I wouldn't think this is a good match.  Maggie's seem to need a muscle amp with lots of current, and I think a lot of purchasers are disappointed when they try to make a smaller amp work--me included.  I had a well-respected 100 watt Sansui, but not enough grunt.  I've never seen them demoed with a low power tube amp, which should be a clue.
A friend and I stopped by Shelly's Audio in the San Fernando Valley one day back in the 80's. They had a pair of 3.1's in the showroom and were driving them with a pair of VTL "Tiny Tots" ... tube amps putting out only 25 watts per channel. Gotta say, within the power range, the sound was simply glorious. You wouldn't want to use these amps with Maggies on a full time basis of course, but as a simple experiment, it was really good. 

Those little VTL Tiny Tots are as rare as hen's teeth now.