With 2-3k to spend you can build a very powerful rig. I would go with a PII 965, a good AM3 motherboard, 4-8gb of DDR3, a pair of HD 5870, and a good cooling system. You could also get 2 HD 5970 but I don’t think you need all that (I don’t think anyone needs all that) and it would cost half your max budget. If you think you need a better chip after a few weeks, grab a Thuban when they come out.