and the Mobo is an AM3, so there's no need to change the motherboard,
either get a Athlon II x4 640 (100USD) or the Phenom II x4 955BE (140USD)
The Phenom should have more juice overclocked due to it's L3 cache though
I'm saying he will need a new motherboard with the next gen cpu's coming down the turnpike. For now, I would have to agree to go with the Athlon II 640 as I have 3 of these and they perform exceptionally well. If you can't wait to upgrade that would be the best path at this point performance/cost wise...