Witch mutherboard and CPU would be good to OC

I went with the:

ASUS M4A79XTD EVO AM3 AMD 790X ATX AMD
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131402

and

AMD Phenom II X2 550 Black Edition Callisto 3.1GHz 2 x 512KB L2 Cache 6MB L3 Cache Socket AM3
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103680

For $200 or so combo, I don't think it can be beat...and I am in absolute love. I haven't overclocked much yet, @3.4GHz right now, but it's a breeze to do, and still runs cool as a cucumber on stock air. I hear of people able to get them to 3.9GHz or so, but you would definitely need a cooling upgrade if you went that route. Some people are also able to unlock all 4 cores at a fairly high rate. I have yet to try, but will eventually attempt it with some better cooling.

Impressive. But so is the core voltage.