Hope this is the right place to ask.
I notice on the Nvidia site that they have a bunch of tools that could be useful in the creation or porting of games.
See http://developer.nvidia.com/page/tools.html for a list.
Im not sure if they only apply to DirectX 9 or whether any of it is compatible with the xbox. But if Im not mistaken the xbox uses Nvidia.
The Content Creation tools look interesting although some of the tools you can already get with the xdk.
Thought it might be of use to anyone.