So many things I agree with here, and disagree. Having efficient speakers opens up so many more choices in amps. I can drive my Crites speakers with the XA25(really 80W) to at least 105dB continuous without leaving Class A. Clear as a bell. Granted my ears can't take it but it sounds good. Having subwoofers does help your amp breath easier. So many variables here but I think it is more a mismatch of components than the sizing of the amp. I don't see why you need a boat anchor megawatt amp with efficient speakers. Not saying it won't sound good, it will. There are many examples of efficient speakers and even more examples of nice amps so we all should be able to find a match.
enough amplifier power
I am curious as to why so many people think that their amplifiers are powerful enough for their speakers. I use a Yamamoto A-08S--around 1.5 watts output. I use it with a Fostex F-106ESR. The combination is a little ragged at low volumes, but beautifully immediate. Distorts awfully at anything approaching a decent volume. I see people using 20-100 watt amplifiers with medium efficiency loudspeakers. I do not see how this can work any better. If you work out the math, most loudspeakers need 200-500 watts minimum. That is not even taking into account low impedance loudspeakers. Do people not know what distortion sounds like? Or, compression either, for that matter? Please enlighten me.