I think Audiokinesis brought up an important point about playing music at lower volumes: the lower the volume the less bass and treble the human ear/brain perceives in relation to the midrange frequencies. This is compensated for with switches on a lot of mass market equipment ('loudness' switches, etc.) but never seen on the higher end preamps and integrateds.
I definitely agree, though, that each amp/speaker combo has its own sound or personality regardless of wattage.
I definitely agree, though, that each amp/speaker combo has its own sound or personality regardless of wattage.