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.