JohnK,
I agree that an 'amplifier' should do nothing more than increase the amplitude of a signal and therefore should not influence the 'sound'. However, a reciever is not just an amplifier, it converts digital signals to analog, it decodes information into discrete channels, it applies 'tone' to the signal (equalization), it applies varying amounts of harmonic distortion and it amplifies as well. Therefore the scope for changing the 'sound' is quite great. I recently switched from a Yamaha 5560 receiver to a Denon 3803, and believe me, they 'sound' different.
