I don't think there'd be much if any difference in sound quality between a "reasonably priced" pre/pro and one of the top-of-the-line receivers.
If the receiver is the weakest link in your system, chances are you would hear an improvement in sound quality. There are many people who once owned top-of-the-line Denon receivers mated to an amplifier, singing the praises of a "reasonably priced" Outlaw or Rotel pre/pro, after they switched.
The professional mag reviews tend to back that up.
Maybe I missed it. I haven't seen a magazine review that says a top-of-the-line receiver sounds as good as "reasonably priced" pre/pro's from Rotel or Outlaw. The top-of-the-line receivers often have more features.
[This message has been edited by Will (edited August 13, 2002).]