I have an Phenom II X2 550. Couldn't unlock the extra cores cause I was sporting an Asus M3A78-T MB. Well, Asus just came out with their latest 1403 BIOS and just turn on ACC and Unleashing and there ya go.
I now have a Phenom II X4 550 BE running at 3.7 smooth as butter. Not bad for $100 USD's. Your CPU-Z will call it a Phenom II X4 B50 (have no idea why).