Intel i5 2500k, has an unlocked multiplier so you don't need to worry about ram for your OC. If you want to spend a little more i7 2600k. Link
ThermalRight Archon is probably the best air cooler available now (if it fits).
Of course if you are willing to wait a few months you can get an Ivy Bridge CPU and the next gen ATI or NV GPU of your choice.