I have a Kenwood receiver, model VR-616 that came with a home-theater-in-box. It claims to have 100w/channel and the subwoofer amp is on board. I replaced the speakers that came with it with the package with Polk R15s and a CSi20 center. I also bought a powered subwoofer and connected to the speaker inputs from the receiver. It sounds fine. My question is this: will buying a new receiver such as the Onkyo SR501 or SR601 make enough of a difference in the quality of movie sound? Is it worth the bucks? I use this system for 99% home theater/movies. Last question: Is there a receiver/amp that is specifically made for 6.1 home theater, i.e. no AM/FM tuner, no phono inputs, no DPS modes, etc.?