The greatest impact on sound quality will be your speakers, room acoustics/placement and the quality of the recording the speakers are reproducing.
The most noticable way receivers can affect sound quality is through the use of tone controls or running the amp past its power requirements which introduces distortion or "clipping" (not a good thing).
If two different receivers are level matched, tone controls bypassed and neither is introduced into clipping, the differences would be very subtle as compared to listening to 2 different sets of speakers, or the same pair of speakers placed in different rooms.
