Most 3D modeling and renering programs right now rely solely on CPU power and speed for rendering images. So, the faster the processor the better. If you have a program that can make use of multiple --- dual-, quad-, or X-core processors (which Anim8or does not, so far) --- render times go down some more. And some programs support using render "farms," multiple computers with multi-core processors. And be sure to get enough memory to accommodate the polygon complexity you're after.
On the flip-side, some programs are looking into harnessing the processing capability of the newer Graphic Processor Units (GPU) on high-end graphics cards. So, in a way, it kind of depends on the type of work you want to do (low- or high-poly), and whether you intend to stay with Anim8or, or migrate to Blender, LightWave, 3D Max, or higher-end programs.
