I'm in the exact same boat as him (Sharp tv, xbox360, surround sound). We're trying to use the HDMI video/audio outputs from the xbox, while running the optical audio output from the tv to the DD5.1. There is the option of downgrading from the HDMI to the component cables and optical directly from the xbox, but preferably we'd like the HDMI connection (xbox --> TV) AND the optical out (TV --> DD5.1). The Sharp seems to not allow for optical output with an HDMI input to run simultaneously. This may have a fix via firmware update, though I don't have the means to check.