Onkyo probably have the best low-cost receivers around. I have one myself with HDMI for my xbox, ps3 and htpc for video and optical from my htpc for audio. Works like a charm
Amazon had some good deals if you wanted to take a look. Depending on what you are looking to spend, I saw the full 7.1 receiver AND speaker set (THX version) for about 750-800 bucks. It used to be around $900 or so before. Stand-alones are probably around $300 or so to start with and go up from there.