the est bang for the buck would be an AMD FX8320 (commonly on sale for $125ish) and an ASUS motherboard.
m5a97 r2.0 would be ok to save $ (about $75 after rebate)
m5a99 better if you are more into overclocking ($100 to $110 after rebate)
Never really done any overclocking. With the speed of that cheap, is it really necessary? Does it yield any big advantages?