I just bought Onkyo SR601, I was wondering how Polk R50's match this receiver(these are on sale for $200/Pair in local fry's, that is max I can spend).
I have this as my music set-up and am quite happy. However, if you listen to bass heavy music, I will warn that you may find yourself in the market for a subwoofer since the bass was not terribly strong with the set-up as you describe. I have the low end Polk subwoofer and after about 25 hours of burn-in, everything sounds great. I will again note that this set-up is 100% for music listening. I have the 701 for theatre use and would be hard pressed to say that I would not be just as happy with the 601 and the R50's in this regard.
BTW: I paid $299 for mine and it is a definite deal at this and your price. I still want the the Polk RT's (higher top-end and stronger bass response) but I am highly satisfied for now.