Second, there is no such thing as an amplifier being overpowered for any
set of speakers. Period. Musical transient peak demands typically can
require 100’s of watts to the speakers. I doubt your class D amp of 125W
RMS is up to muster.
Actually there is, but if the speakers are only 94 db and the amp only 125 watts, the amp isn't too much power by any means! If a class D amp, I would want more power just to make sure I never got near clipping, a fundamental difference between tubes and solid state (including class D).
Too much power in most cases means that the amplifier is operating in a portion of its low power region where its distortion is actually higher than at higher power levels (typically this is about 5-7% of full power with many push-pull amps). The only amps that I know of that don't have this property are SETs and the OTLs that we make, where the distortion linearly reduces to unmeasurable as the power is decreased.
Its that first watt that's the most important!Regarding critical listening, my amps are on all day and a good portion of the night as well- and I can't say that all that is spent in critical listening. But I've come to expect a certain level of competence out of the system and if its not doing it, my listening gets pretty critical real quick! So tubes all the way (at least for now- we have a class D amp we're brewing up; its got a pretty high bar to meet).