I had the same budget ($500) for a receiver and ended up deciding on the Yamaha RX-V661. I haven't received my speakers or the receiver yet, but from all the research this is the one that appealed to me the most and I feel confident in my decision.

Here is the owners thread from avsforums which was extremely helpful in my research. http://www.avsforum.com/avs-vb/showthread.php?t=822161

I was also considering the HK AVR-247 and the new Onkyo (605 or 604, can't remember which). After reading through all 3 owners threads at avsforum I had a better feel of thier real world performance with all levels of user experience.