Also consider getting the Biostar TA790gx 128m motherboard, due to the motherboard bios by enabling ACC option alot of people can actually unlock the forth core of the x3 720. And once that's overclocked its a **** of a cpu for the price. This board is cheaper then the gigabyte and is better, has great overclocking potential, of course if you have the money go for a x4 940 but otherwise drop either into this board and you will get some great overclocks.
Newegg.com - BIOSTAR TFORCE TA790GX 128M AM2+/AM2 AMD 790GX HDMI ATX AMD Motherboard - AMD Motherboards
Phenom II X3 - Enable and unlock the 4th core from what i have seen most people have had success mainly on this board so why not give it a try. I cannot believe the core is just disabled and not physically cut off.