The only thing you'll need is the ATI DVI-HDMI adapter for your 4850. That card still supports audio over HDMI, and the adapter allows the conversion.
Or, you could also just use the built-in S/PDIF ports on the mobo and connect either one (COAX or optical) straight into the receiver. If you're just gaming and not using it as an HTPC, S/PDIF will work just fine (and probably less hassle).
Yeah, because we all know S/PDIF is superior to HDMI (wallbash)
If you read the original post, he's currently using his PC for gaming, not HD audio and HTPC use. If HD audio output isn't a consideration, S/PDIF is superior to HDMI. Why, you might ask? Because they offer the exact same audio capabilities in this situation, but there are no adapters necessary for S/PDIF. There are no handshake issues, and you only need to troubleshoot audio, not both audio and video if there are problems.
To the OP,
If you go with the HDMI solution, just be aware that you'll be effectively outputting to 2 monitors at that point, so a little extra configuration will be necessary for watching movies.
That's cool. I don't mind some things going wrong and having to troubleshoot. I'm just an audio idiot and figured i'd get some advice, mainly because my color vision sucks major b@lls and having to figure out the ports on the card/receiver can be a real pain for me.
I already output to two monitors at the moment, so I guess the 19'' can take a backseat when I want the TV involved.