For that kind of money I would set up a render farm. One computer with great specs (go for Quad, 4 Gb of ram, as much hard disk space as you like [and an external backup drive] and a simple graphics card [all you need is good Open/GL]) and 4 computers with reasonable specs. Building the scene won't change (that just depends on the speed of your CPU [it will only use 1 core anyway]) but rendering will improve a lot (and you will be doing that a lot).

It will need an internet connection but make sure you keep off anything not needed, never even use a browser on your graphics box.