I'm confused. The manual implies that the STR-DG800 is HDMI pass through - i.e., if you connect an HDMI source to it, you also need to connect a separate digital audio cable to the receiver in order to get surround sound from your speaker set-up. I say this because of the NOTE at the top of page 30 ("When a playback component connected to this receiver and this receiver connected to the TV by HDMI, the sound is output from the TV speaker only."). Your post OTOH implies that the XBOX is hooked up just with an HDMI cable (no separate digital audio connection). Do you have a surround sound speaker set-up (for example, 5.1) or are you just using the TV's speakers??