I think the DECISION between AVR vs AVP is about PERSONAL preference.
My PERSONAL thoughts on this subject:
Just because you own "separates" doesn't mean they will sound better or do anything better. And if the quality is worse, they may sound worse than AVRs.
If you're gonna go separates, then you can't go cheap in the first place - like cheaper amps.
For AVPs, bare minimum is the Yamaha CX-A5200. More expensive would be Marantz AV8805, Anthem AVPs, Monoprice HTP-1. Higher up would be DataSat and ATI ATP-16 (once it is released
). Then even higher up would those $20K AVPs.
For amps, we're talking ATI (and amps made by ATI), Legacy Audio, Parasound, Anthem, Rotel, Classe, etc.
Otherwise, just stick to the simple life of AVRs. They sound great. They measure great. They are a convenient one-piece solution.