Programs render 1 of two ways, Software rendering or hardware rendering. Hardware means the program is streamlined to run through standardized architecture (eg: GPUs in cards) in order to give a high speed response to inputs. Video games on computers and consoles are use hardware rendering.
Software means that the program is emulative of the factors that need calculation. 3D Programs such as Maya, Softimage XSI or 3DS Max when they render, use software rendering to shove things like Radiosity, Alpha sampling, anisotropy or whatever-have-you through the pipeline to result in the final image. While in-program viewports use hardware rendering in order to get prompt input-response for scene and model interaction, the final result is ultimately software rendering, through the computers main Processor.
While lots of juicy Graphics cards would get what you need for gaming, sheer brutal number crunching from a brawny processor is what one would need to render things quickly when 3D modeling. That's how I stand on when and what I need for my computer parts.