Whenever I've upgraded to a more powerful amp, it's also been an upgrade to a higher priced unit with more sophisticated design and construction, so my observations might not be applicable, if you are comparing two amps of similar quality but differ only in their power output.
Having said that, for each upgrade I've found the system sounds like it has more "air" around it, the stereo image and sound stage is improved, and usually the bass is more defined. I upgraded from a 35 watt NAD to a 180 watt NAD, and the new amp just didn't sound like it was exercised that much, sort of like the lower powered unit was "struggling".
Having said that, for each upgrade I've found the system sounds like it has more "air" around it, the stereo image and sound stage is improved, and usually the bass is more defined. I upgraded from a 35 watt NAD to a 180 watt NAD, and the new amp just didn't sound like it was exercised that much, sort of like the lower powered unit was "struggling".