You might want to include your budget and plan for this sytem. You also might explain why you are specifically choosing Nvidia. If you don't care about physX, you might like ATI as an alternative, which currently have the top end video cards.
It would be great if you were a little more specific, but the top monsters are the Intel Core i7 Processors for LGA 1366 and ATi Radeon 5850, 5870, 5970 video cards. However, this would be parts of about a $1500-2000 computer.
Say you had a budget of about $700-750, I'd try an AMD Athlon II X4 quad core and an ATi Radeon HD5670 or 5770.