I'm surprised nobody's recommended Intel. Right now the Core 2 Duo's are more energy efficient and faster than AMD's at the same clockspeed.... I'm not sure if AMD still has the price advantage but if you're going to be paying for a high-end CPU why not get the current leader in the game? Also, it would probably go better with a GeForce since AMD is now going to focus on coming up with ways to exploit their new property (ATI)...
P.S. I seen that the 7600 GT's are going on clearance now for about USD $40, so get them while the getting's good (PCIe)