Crap, didnt notice the cpu was oem.
Any am3,2+ hsf would be fine, **** steal it from a freind
. Or just get this one, it's abit faster and has a fan for $20 more:
Newegg.com - AMD Athlon II X4 640 Propus 3.0GHz 4 x 512KB L2 Cache Socket AM3 95W Quad-Core Desktop Processor ADX640WFGMBOX
The mobo is just fine for the x4, don't know the quality of the board, but it will last and do what you need. All mobos are pretty much equal at nthis price.
The x2 will be plenty, the x4 will be plenty in the future.