You probably don't need a crazy computer for FRC CAD. Our team's CAD models are likely larger than average and plenty of the computers at our lab with older processors and less than 2GB of RAM handle them fine. A nice graphics card, however, can make all the difference. A nice Quadro card can make an okay machine scream for CAD.
Search around on eBay for old workstations. You can get a great machine for a great price. We have at least one of these in our lab and it's great. Searching
"workstation quadro" would probably be a good start. Listings change frequently so if you don't see what you want, look back soon. You can likely get a couple decent machines for sub $300 each.