I’m not looking for a game engine. Simply a few classes that enable 3D and has a level editor attached.
XNA.com has a few samples, probably using Blender. I’m more curious about something that could say, take Quake Engine levels.
A web search for “XNA bsp importer” brings up some good information, such as http://martincaine.com/xna/optimizing_my_bsp_loader