Thanks Bigboss.
My only concern with hooking it up "traditionally" (Xbox HDMI to receiver, receiver HDMI to TV) is the ageing HDMI profiles.
The Onkyo is only HDMI 1.3 - the new xbox is HDMI 2.0a. 3D is not a massive issue - for that one time I want to watch Tron, i'll hook it up directly...