I have also thought about this idea. One of the first things I thought about when I heard the receiver would have both HPNA and Ethernet on board.

Something to consider, though: Since you already will be having ethernet-only devices such as the Xbox and the PVR, then why not just run some real ethernet cable? Problem solved, no hacking needed. Besides, I would think there would be performance penalties associated with using the Rio Receiver as a router (it's CPU isn't all that beefy).