LOL finally a question even I know the answer to.

Here's what your gonna do. First take the hdmi out of the xbox. Then take that into an hdmi switch. Most hdmi switches also pass out optical audio via toslink. You take the optical out of the switch into the preamp. You then take the hdmi out of the switch for video only into a component video down converter. Out of the down converter via component to the display or video input on your AVR and the circuit is complete.

Easy like Sunday morning.