What is your experience with amp power?

@spaceguitarist : Excellent article! My French has become almost entirely unusable (I last studied French in college almost 40 years ago), so I had to resort to the translation function, but the information was spot on. My experience with “rated power” of various amplifiers has shown this info to be true. See, we can agree! Lol. Thanks for the link. 

Using examples such as: “Amp A @ 600 w/ch sounds better than Amp B @ 150 w/ch shows that more powerful amps sound better” is an unreliable argument. It may in fact be 100% true, but is it solely due to Amp A’s higher maximum power rating? No. Also, the idea that a 200 w/ch amp plays 3dB louder than a 100 w/ch amp only holds true when each amp played to its maximum output. At any listening level below the maximum output of the lower powered amp, the output is unaffected by the maximum rated power (all other factors equal, re: input sensitivity, power supply, design, etc.). Two amplifiers using identical components, but configured differently so one outputs 200 w/ch rated power, and the other outputs 50 w/ch won’t sound different because of rated power, unless the listener exceeds 50 watts. For example: If you are listening to music and using 25 watts to achieve the volume level you desire, it matters not whether the amp in question maxes out at 50 watts, 100 watts, or 1000 watts… because you’re only using 25 watts for this level. There WILL be a difference if one amp in the comparison is designed with a stronger power supply, regardless of its power rating. 

Here is my experience with SS and tube power on a pair of Nola Ko speakers. 1st I had a MF m6 series 230 wpc SS amp running them. A little forward that would fatigue my ears after a couple of hours. Next I used a 75 wpc KT 88 tube amp. I thought now I'm moving in the right direction. Much more refined sound quality. And I can listen for much long with no listening discomfort. Next amp was a 20 wpc tube amp with el84 tubes. Now much more open and airy sound and still quality bass. Now here is the big surprise. I tried a 8 wpc single ended amp on them. To my surprise this was the overall best sound quality amp for my Nola Ko speakers. This Wee amp can push them to 80 db in a 24' x 18' room very easy for many hours on end. And the plus side of it is no listening session is to long now. 

Considering that you use a well designed amp that can provide 6dB dynamic headroom : for Hifi listening you will **NEVER** need more than 2x50W RMS/continuous 0.5%THD-20Hz-20KHz ( 6dB dynamic headroom ~ 2x200W dynamic power) to drive the most demanding speakers (most demanding speakers are usually the small "low sensibility" bookshelves)

If you need more than 2x50W RMS : then you are either doing "sound system" - not Hifi (it’s not bad to seek "sound for the whole room", but it’s not Hifi listening); ... or it means that your amp is not designed for Hifi (Usually high end Hifi amps have a good dynamic power, but I’ve seen amps costing more than 10K$ with specifications that I wouldn’t validate for Hifi listening : these are sound system amps).

For sound system : the amp should provide at least 2x200W RMS at less than 0.5%THD, but it varies with the room size , so you may wan 2x500W RMS for a very large room. Room size is only a matter for "sound system", for Hifi room size is not relevant as you will always listen at 3~4 meters at the sweet spot in Hifi !!!! (else it's not hifi).

Everything is explained here :

Excellent discussion. Here’s a musical take.