I used the Gefen DVI Detective in the past, when the ATI drivers were immature, and you had to turn on the tv before the htpc to get a picture (this has now changed and i no longer required it). Now they have an HDMI version. Just make sure by visiting the forums that it handles audio properly (I'm sure it does). You'll need to plug the detective directly into the tv and get it to learn the EDID codes, then you can run HTPC -> Detective -> Receiver > TV.