Is more amp power always better...?

My thinking, a speaker having a true 89dB sensitivity to be used in a 10'x11' room can easily be by served by an amplifier providing 50wpc at 8ohms and 100wpc at 4ohms. 

My advice, search for an amplifier that mates best towards the presentation you desire rather than the power it delivers. Low watt SET amps an exception.  

The numerical value given for damping factor is 8 divided by the output impedance of the amp—the lower the impedance, the higher the damping factor.  A typical SET amp can have an output impedance of 2 ohms or more, for a damping factor of 4 or less.  This relatively high output impedance interacts with the impedance of the speaker, which varies with frequency, and thereby affects the frequency response of the speaker (the lower the speaker impedance, the greater the change in frequency response.  Thus, SET and other tube amps with high output impedances are best used with speakers with a rated impedance of 8 ohms or more, and with an actual impedance curve that is relatively flat.  Any damping factor above 8 is probably high enough to be irrelevant.

So the ASR Emitter 1 might be a good option. I own the ASR Emitter 2 Exclusive and they sound great with a pair of Quad 2905’s. Quad 2912’s would be the same. I have to share with you however my experience when I matched the ASR with a pair of Monitor Audio GS 10 bookshelf speakers. The amp was just too much for the bookshelves. It sounded like a Tasmanian Devil was trying to break out of the cabinets. When I bought the Monitor Audio’s I was told that it was impossible to blow them up but I blew both a woofer and tweeter. I then paired the Monitor Audio’s with a Rega amplifier and they were fine.

Definitely not always.  We also can't really say this is true about having more damping factor. 

The amp/speaker match up is important as is the quality of the first few watts of power.   There are definitely speakers with troublesome impedance curves that like big amps with low output impedance, but also large speakers with big woofers that can benefit from high output impedance.  See Nelson Pass's writing for the latter.

The SET folks say that the first watt is the most important. Some of them get by with 5 and I’ve heard even less. 
 

In other words, quality over quantity but you need enough to drive your inefficient speakers. 

I have a Hegel h160 but was looking to downsize. Found a Keces e40 and for its size, price and power, I don’t think there’s anything that can outright beat it for its SQ within its power limits.

I have had less expensive higher powered gear in comparison to it and it beats them in SQ. Close enough to the Hegel at the SPLs I listen at on my dacs, speakers and room at a fraction of the cost...and size.

Want smaller and lighter and I am getting it. Someday, I would like to try a van Alstine Set 120 though, among a few others amps, speakers and dacs but no interest any longer in spending on high dollar items say over $3K and above.

The Keces drives my Opticon 1 speakers without issue but would be wary of floorstanders of low impedance or speakers that drop well below 4 ohms, or if you need high SPLs, otherwise its fine and can compete with much more expensive gear. Getting marginally more power and/or performance will cost up to double the price, or more.

The Keces works well with all my other speakers too.  The hegel grabs the little opicons so much the bass doesn't come thru as well, just too much for that little woofer.

I have a pair of very efficient speakers at 12 ohms impedance playing in a modest listening space and the best sounding amps are those of low wattage class-A.  I've heard a number of class-A and class-A/B on my speakers, even those of class-A/B with the first several watts in class-A.  With really good and well-designed class-A/B amps, usually their first several watts are class-A and for many speakers at moderate volumes don't exceed much past class-A..  I have two First-Watt class-A amps (10 - 20 WPC) that are quite articulate and have plenty of power to handle my listening levels.  That said, you will need more power than those can deliver for your 89-db speakers especially at higher volumes.  Also, it depends on how well the amp can supply current if the impedance is low.  If your speakers are a true 89-db, they are playing at 89-db with 1 watt of power at about a meter from the drivers.  That level goes down about 7db at the listening position to about 82-db.  When I'm listening, most times, I like listening between 85-db and 95-db.  Any higher in my listening space and everything starts to get jumbled up sonically.  Looking in your case at going from 82-db to say 95-db at your listening position, you have to have enough power to drive the speakers to that level and higher on peaks.  Thats a 13db listening range.  With your speakers 82-db at the listening space is 1-watt of power and at 94-db would be 16-watts.  I have read that to be safe, you should have enough power to drive ~10-db above your normal listening levels for peaks.  That would equate to about 128-watts of power/channel.  Let me preface this with some caveats...  That assumes you have speakers that are 89-db and generally run no less than 4-ohms minimum impedance.  You'd need an amp that can deliver a good, clean 128-wpc into an 8 or 4 ohm load.  If your speakers dip notably below 4-ohms, you'd have to make sure the amp can deliver enough current to get to the 128 WPC.  Please note that my information above is based on a number of assumptions.  I personally don't need much power as my speakers are 106-db efficient so are operating most of the time in 1-watt or less of power !  I can get away with flea-watt amps easily.  Good Luck on your amplifier search !  

You can convert RMS wattage ratings to current (amperage) easily enough but that isn't the entire story wrt the quality of the power supply, which is important in supplying short term peak power without distress.  Making sure to have sufficient peak power for dynamic musical passages is probably why Ralph recommends exceeding the speaker's rated wattage.  However, I don't always trust those "ratings", which is why the SPL calculator I posted can be useful to evaluate power needs for your specific speakers and room.

Good point on doubling power into lower impedance loads but those numbers get played with by manufacturers too.  Take an amp rated at 200wpc @ 8 ohms and 400wpc @ 4ohms, does that amp really double into 4ohms, or is it actually a 250wpc amp that provides 400wpc into 4ohms?  Does it really matter?  Simply purchase an amp that is large/powerful enough to drive your speakers to the levels you want to listen on the music you like to play.

When I think about "quality watts" as discussed here, I am reminded of the Lamm 1.2 Reference amps that I owned.   Those Class A hybrid amps were rated at only 110/220wpc into 8/4ohms, when set to their high impedance setting, and the same wattage rating into 4/2ohms when set to their low impedance setting.  My speakers dip to just below 4ohms at certain frequencies and those amps definitely sounded better at the low impedance setting in my system.  They were not powerful enough to convincingly drive my speakers to the SPLs I wanted to hear but, within the volume levels they provided, there seemed to be no loss of dynamics or tonal color.  IOW, they sounded really good, but simply ran out of steam at a certain volume level.  I have never heard another amp respond like that in an underpowered situation.  Most I have heard begin to sound stressed and thin well before their limit. 

@dunkin The most important thing is that the amp have good clean reproduction at a low power level like 1 Watt because even with your speakers that will be a common power level.

The class of operation, the amount of power isn't important as long as the amp is musical and plays nice with your speakers. As a general rule of thumb its not a bad idea to have a bit more power than the speaker needs so you'll always have headroom. So if the speaker's max is 70 Watts a 100 Watt amp is a good power level.

Some designers claim that paralleling multiple output devices to get higher output degrades the sound.  The original Dartzeel amps were based on the philosophy of minimizing output devices (only two were used per channel), but, demands from the market for more than 100 watt/channel made them abandon this philosophy. I don't know if there is any truth to this claim.  But, many years ago I heard two Rowland amps that were very similar in design, but one was rated at something like 50 watts and the other 200 watts per channel.  Both were used to drive somewhat challenging speakers (if I recall correctly, they were Maggies).  At the not extremely loud volume I heard the combinations, I actually preferred the lower powered amp and so did the owner of the store that demonstrated the amp/speaker combination.  Who knows what other factors might have been involved, but, in this case, the lower powered, and cheaper, amp prevailed.  

When coupled to high efficiency speakers, my favorite amps are almost always low-powered tube amps  I currently run a 5.5 watt per channel pushpull pentode amp.  My other amp is a parallel single ended amp that puts out a whopping 6.5 watts per channel   One of my all-time favorite amp is a pushpull triode amp that I think puts out 8 watts per channel, my other favorite is an output transformerless amp (giant four box affair for stereo) that puts out something like 30 watts per channel.  

Amplifier power ratings: WPC in isolation is meaningless , it’s current (amps) that matters.

If your speakers are demanding to drive you’ll need a suitably muscular amplifier to support them.

Don’t look only at the headline power figure - see what happens when the impedance drops to four ohms. If the number nearly doubles, then your amplifier has good high current delivery and will be capable of driving more demanding speakers.

Better amp is always better - watts are deceiving in my experience.

For example a 80 watt Audio Research Company integrated amp and it shocked me in the dynamics, clarity and powerful bass drive.  It sounded more powerful than McIntosh C462 to me.

I've currently own Moon 860A V2 which is 250 watt amp and it's an upgrade from Moon M400 monoblocks rated at 400 watts.  The 860A V2 has larger power supply (it's a dual mono) and more capacitance capacity and able to reproduce music at a finer level of detail with finesse as well as bass drive.

I agree more power is better though theirs more to understand the power of amp than just the watts per channel.

In my experience, the larger the transformer is in the Amplifier, the better it will sound (Solid State).

Class D is a bit different there, but a quality power supply in the Class D is important.

If I have this correct, the larger the transformer, the more current it can deliver (I may be wrong here) - I do know that the Dyn’s that I have are current pigs, and they sound phenomenal with high current amps and lean with lower current amps.

I have heard a lot of class D lately that sound really good.

My next Amp-Go-Round is going to be Purify’s with a tube input buffer stage (If I have that r=terminology correct).

In summery, like an above post stated, ‘Heavy is Good’ - most of the time.

My 2 cents

More watts do not make for better sound. If that were true, a Decware Zen Triode would sound like absolute garbage at a whopping 2 wpc yet it does not. It continues to baffle me what some people believe despite any objective evidence. 

“Quality watts” is a catch-phrase, in that any manufacturer will tell you their amps provide quality watts. It is simply another way of saying expensive amps often sound better than inexpensive amps and, given their speakers, room, music, and listening habits, some listeners prefer an expensive amp that provides less power to a more powerful but less expensive amp. Of course, if your budget allows, figure out your power needs and then buy the amp that meets those power requirements while sounding best to you.

Listen for yourself and decide on the type of amp that sounds best to you. Decide for sure that you plan to stick with your current speakers. Tube watts, and Class A watts can be expensive. A SS amp, or amps, will be less expensive to provide the amount of power you need for your medium efficiency 89dB speakers. Consider the type of music you listen to, and the volume you listen at. Do you like to occasionally rock out and, if so, do you want enough power and headroom for a realistic portrayal of the crescendos? Do some research on sound pressures for your chosen music and listening habits and then use something like this calculator to verify how much power you need. I would guess at least 100 wpc with 200 wpc being optimal, if you want the ability to occasionally crank it up.

Try Class A amps if you must but IME of owning several, they are generally over-hyped for the sound, the inefficiency and heat, and the cost per watt. I would look for a well-built, well-regarded, class A-B amp that provides the power you need. Go listen to some amps, if not at a dealer, then in your friend’s systems, or at an audio show. Or, if you must, read the reviews, buy something, take your chances, and sell it if you don’t like it. You won’t be the first or last to do that, and neither was I but, relying on reviews and feedback from others can be a longer road to satisfaction than hearing stuff for yourself before buying.

@OP A power amplifier is basically a modulated power supply, so the quality the amp's power supply is more important than its power output. Quality watts don't come cheap so you should not buy a bigger amplifier than you need. 60-100 high quality watts supported by robust current delivery is quite adequate for your setup.

@zlone "Pretty sure I rarely cross that threshold these days.". 

People don't often comment on these threads about the volume LEVEL they want or need to listen to music.  "These days", I don't listen at higher volumes any more myself. Don't need to any more. With quality amplification can hear everything well enough without having to turn it up a lot louder.  

@decooney My pure Class A solid state 50w amp with mosfet opts (always on), sounds better than my other Class AB amps where the first 10w was supposed to be Class A.

Good point, pure Class A is another option. I am guessing that amps designed that way are simpler and on average probably deliver better sound. I considered it myself, but opted for a high current amp with 18 watts of Class A on the front end. Pretty sure I rarely cross that threshold these days.

@zlone Lots of good advice here. If you can find an impedance graph for your speakers and see that they spend time at 4 ohms or below, you will want to ensure that the amp doubles or comes close to doubling wattage when impedance drops to that level. Another thing you may want to look at is how many watts of class A are available before A/B kicks in. But as many have already stated, specs alone do not tell the whole story, in the end it has to sound good to you.

Channeling @atmasphere who might chime in on this topic, and explaining more about "how" and "why". My pure Class A solid state 50w amp with mosfet opts (always on, biased full Class A), sounds better than my other Class AB amps where the first 10w was supposed to be Class A. Not sure why exactly. I just know the pure Class A just sounds better in my setup once everything is good and warmed up - fwtw.

If you want to see  the impedance curve you can use Room EQ Wizard with a home built wiring jig to measure it, or you can buy Dayton Audio DATS (what I use) to chart it. 

Lots of good advice here. If you can find an impedance graph for your speakers and see that they spend time at 4 ohms or below, you will want to ensure that the amp doubles or comes close to doubling wattage when impedance drops to that level. Another thing you may want to look at is how many watts of class A are available before A/B kicks in. But as many have already stated, specs alone do not tell the whole story, in the end it has to sound good to you. 

Type of quality power matters too.  It's not just about quantity of power for me.   

Rotating now between my tube amps to my solid state amps, for many years, formerly i used decent 200-300w dual mono Class AB amps. Nice full sound, yes. True Class A sound, NO.  I'm back to experimenting with this a lot again recently.   

Now trying the upgraded 50w Class A solid state amp again this winter. Its a bit more lean first 45m of warmup. Once its fully warm and toasty past 60m to 120m, the Class A 50w SS amp is more magical and engaging to listen to than my more powerful Class AB 200-300w amps were. Particularly at low volume levels too. 

Would I say the more powerful solid state amps sound better in this case?  No.  

There are days the Class A 50w solid state mosfet amplifier also puts my other two Tube Mono 100w amps to a challenge of sitting for a while longer. 

IMO, Amp / speaker pairing is a tough nut to crack. So much comes into play. Listening preferences I think is a major factor that gets overlooked. I’ve had a 200wpc beast that didn’t sound good unless it was pushed to volume levels I don’t find enjoyable. Whereas on the other hand I’ve had 75wpc do the job rather well. Definitely do as much listening as possible before pulling the trigger. Good luck!

this is one of those "all things being equal" situations. where yes, more power is always better if the amps are otherwise equal. the reason for that is that amps sound better when they have headroom, meaning they are operating in their lowest stress point and lowest distortion point, which allows them to give the music ease and authority.

OTOH it’s rare that all things are, in fact, equal, between two different amps. some less powerful amps have simpler, more musical and refined sound than more powerful amps do for various reasons. so even though an amp might have an easier time with some speakers in some rooms, you cannot paint with a broad brush since amps circuits vary.

there are some obvious amp <-> speaker pairings in large rooms that are not going to work very well. so sometimes you really do need that more powerful amp. but your goal should be the right amp, not necessarily the most powerful.

one other important factor regarding amplifier and speaker matching for a particular room is the type of music you want to hear. if you want 'large scale' and 'very dynamic, complex' music to sound natural and not limited then more power is more significant. if you like small combo or girl with guitar mostly then amp headroom is not as important. if then later your tastes change then the system capabilities might need to change with it and you may need a more powerful amp, or an easier to drive speaker system.

200-300 watts. For example: MC312

I'd say almost always, but too much in excess of necessary may not be needed. 

The simple answer is rarely.  If  you want to seperate  out the real garbage  form the better quality  from a piece  of paper is look on the spec sheet  at the weight.  A friend  years  ago bought a 5x100 watt Sony home theater  receiver  it weight  was less than 5 pounds  it was a gutless horrible thing.  He then got given  to him a old pioneer  receiver  that was 50 watts x 2 and he got something  that had some guts a real power that didn't  blow up all the time it's weight  was around 40 pounds. Better sound. That is a very simple way to make the first cut before  you listen  but if they weight  something  it will be better than a item  that the box and packaging  weights  more than what is inside. A quick way to judge low-fi

I know this is frustrating but I've found that the manufacture's stated WPC has very little to do with true, usable power output.  One really has to do a deeper dive and either listen in person or get information from a trusted source like an informed friend or dealer.

Please don't associate watts with sound quality.    In a 500 wpc amp, if the first watt is crappy, the remaining 499 watts will be crappy.  I have a 40 watt tube integrated amp driving speakers rated at 92 sensitivity.  I can blow the roof off with volume (not important to me).  Most important:  The sound quality takes me places my car can't.

The answer to the title of your post is:  No!

Being a bit underpowered at "normal" listening levels will result in some degree of dynamic compression. The result will not sound "wrong" or objectionable, just not as impactful, or with as much contrast between quiet sounds and loud ones. Severe clipping due to insufficient power at high listening levels is another story altogether. Not what we’re referring to here.

On the other hand, the "wrong" high powered amp will sound wrong to you, which would be objectionable.

So, pick an amp that sounds good to you.

Just like a hot rod , more is better.

You want good quality.

This would give you class A power and enough of it. I'd say this would be your amp.

How many ohm are the speakers ? 
150-200 wpc is a good average at 8 ohms and she be close to double the power into 4 ohms for any decent quality amp referring to SS .

the reserves are good for transient peaks to prevent distortion if playing loud.

with any room acoustic room panels are a big flus to reduce echo, reflections and distortions.

 All the specs. of an amp can help determine whether it is a good fit, but in my opinion the signal to noise and wattage will determine your headroom. For dynamic listening you must have headroom and that will take wattage.

My advice is not to focus exclusively on the watts. A lot of mediocre amps are made to meet a big spec, but not necessarily play well in a system. A better amp and bigger amp aren't necessarily the same thing. All watts are not created equal. You will want an amp that sounds great to you....to do that you’ll need enough clean power to play to the levels you like in your room with your speakers, and that’s always a variable.

I’ve gone the gamut of a big Hafler amp at 255wpc down to a smallish tube amp @ 17wpc triode (on average sensitvity speakers in a large space). I do have a subwoofer, but the main speakers play plenty loud with the small amps, and sound wonderful doing it.

All things being equal, having some power in reserve is a good thing, but power is a poor indicator of how it’ll sound to you. Aim for quality watts with a sufficient power supply and circuit that’ll overcome the obstacles your system poses, hopefully within budget. (used can help cut premium costs down)

yes

Wattage doesn’t equal audio quality.

All things being equal/ assuming you have 2 exact amplifiers (other than their wattage output), the one that puts out more power, say twice as much is going to give you better audio quality. It will not strain as much and will have better headroom and dynamics for a specific output level. Picture a 4-cylinder car versus an 8-cylinder car going up a steep hill.

Keep in mind that most amplifiers are performing at their best sound quality around 15-30 watts of output, regardless of their maximum/ rated wattage output. It’s when you go past those 15-30 watts that thing begin to change. This can be seen on a graph from manufacturers that publish that information or individuals that perform tests and publish them online.

I would concentrate more on the "sound characteristics/ signature" of an amplifier more than on wattage, but if you can have and afford both the sound signature and the wattage, why not?

For what it’s worth, I very rarely exceed more than a few watts (literally) on any of my systems, but have several hundred and even thousands of watts on a couple of them waiting to be used when and if I get that urge to crank up some music, although my desire to do that has diminished with age.

Your speakers are not highly sensitive so going with higher power isn’t a problem, and the less hard an amp needs to work the better. In your case with your speakers and in your room I’d think anything 75Wpc+ should be fine, and I’d focus more on what type of sound characteristics you’re looking for and let that be your primary guide. The only caveat would be if your speaker’s impedance drops below 4 Ohms, then you want an amp with a more robust power supply to comfortably handle the dip(s). In this case and as a very general guideline, the amp should be able to put out at least 50% more power into 4 Ohms versus 8 Ohms. Hope this helps, and best of luck

In general, if you hold the sound quality the same, then yes, and more so for solid state than tube. But not true at the margins of speaker efficiency: low… more important… for high efficiency speakers it can cause problems). Also, unless you are choosing between the same brand and design of amp, then there become so many more variables that the generalization gets lost in other factors.