Mikey, there shouldn't be an audible difference in the situation you describe. Remember that at average comfortably loud sound levels speakers use about 1 watt. Much more can be called for on peaks, but as long as its power capability isn't exceeded, a relatively low-powered amp will continue to amplify the music without audible distortion; it doesn't care that it's working harder, as long as it can still do it. So, no, the added headroom(say 200 watts instead of 20 watts)doesn't result in audibly better sound unless on some rare instance that extra headroom actually had to be used. When the power used didn't exceed say 10 watts the two amps would be audibly identical, unless the 20 watt amp(or the 200 watt amp)was audibly inferior in some other respect, which would be unusual these days. Clean power is cheap.
