I would get a Core i7 with a X58 motherboard and 2 GTX 295's in SLI(from what I can find they are scheduled to be released 1/8/09). If you prefer to stay with an ATI card then i would get 2 4870x2's and run crossfire(the GTX 295's are a bit faster and use less power). Also you're going to need one monster of a power supply to power either config. Getting 2 of either of these card won't even come close to $3000.
http://xtreview.com/addcomment-id-7282-view-GeForce-GTX-295-vs-HD-4870-X2.html