I use Rhino for modeling because it does true boulean operations. Its native format is nurbs. When I convert objects over to a mesh format that bryce can import the filesize of objects can get huge and eat up my ram. I agree with Nukeboy. One of my simplest meshes in my gallery is called temple of raskalon. The mesh is sort of like a set from doom and is all flat plains. The entire object is only 55K, less than an average 2d jpg, but it took 1 day to render. That's because most of the textures had three components and all the ray bounces because I stacked lights inside bumpy glass. You will get more bang for your buck if you upgrade your processor first and add ram second. It's a couple of hundred bucks for this verses at least a factor of ten for commercial cad type modelers. There are some pretty good apps like metasequoia or xfrog that do one or two things extremely well. None of these will do as much to affect the render time in bryce more than getting more speed and space.