CPU for Geforce GTX285

Solution
+1 what elmo said.

the core i5750 is an amazing processor. if you can afford it though, i7 860 is a better choice.

but if you're on a budget an AMD phenom 955 should be sufficient for that card.
I would think that something like an Intel Corei5 750 would be ample enough to power that Graphics processor while leaving you both some overclocking headroom as well as future upgrades in the form of Intel 32nm LGA 1156 Corei5/i7 processors.