Best CPU for a CAD Workstation

Hi there. I'm not sure if this should be in the hardware or software forum as my question is about what hardware would work best with my software. :-D

Anyhow, I've talked my boss into springing for a new workstation for me. I want to get the best that I can get while trying to keep the price around 2k-2.5k.

I've got the whole system picked out. I've just been thinking I ought to check and see if anyone knows what kind of processor would be the best for my application. I run Solidworks 2009 exclusively and I do everything my company needs with that program. My assemblies can range anywhere from 5-200 parts and I've occasionally gone over that. I run it with the graphics settings on high because I like smooth edges. I do not do any simulations but occasionally do some rendering.

Does anyone know what kind of processor would be the best? I'm planning on getting windows vista with 4gig of DDR1066. Should I go with a single core, dual core, or quad core? I know some applications aren't set up to take advantage of multiple cpu cores so I didn't know if getting a dual or quad core would give me any performance gain compared to a single core. I've always been a loyal AMD customer but since I don't have to pay for this system, I would be willing to install Intel if it was going to be a good performance gain for the increased cost.

Anyway, any suggestions?