I bought an RCA home theater in a box a few years ago and it's suited me just fine up till now but with my recent purchase of a high-def projector I figured I might invest some cash in upgrading my sound system but before I do I'd like to know how important is the receiver to the sound quality? My receiver is 650 watts, 5.1, can decode DD, DTS, and DPLII, and it has the optical inputs which is everything I need so if I can avoid upgrading that it would be nice but I don't see much sense in buying some nice speakers (my current ones are crap) if the receiver is a major part of what's sucking up my audio quality.