One thing I wanted to test was the amount of geometry B3D would happily shift with it.
I'm sure I read somewhere that B3D uses lists for triangles. In that case its not going to be as fast as something that uses VertexArrays.
Anyway, LOD is your best friend. Same with Bump-Mapping. Bump-Mapping can give close up objects a nice illusion of fine detail, and LOD can remove triangles that would otherwise not be noticed in objects in the distance. I'd say around 2,000 - 3,000 polygons per character, 10,000 - 20,000 for the level etc. Your probably looking at a complete scene being around 40,000 - 50,000 polys. It also depends largly on what your trying to create.
For RPG games you hardly ever get relatively close to an object so some detail can be left out. In FPS games your often right up against objects/characters/scenery so fine detail is essential to make it look good.