You'll also want a good motherboard if you're looking at overclocking. Ones I recommend:
M5A97 R2.0
GA-970A-UD3
GA-970A-UD3P
M5A99X
GA-990FXA-UD3
GA-990FXA-UD5
GA-990FXA-UD7
Sabertooth 990FX
The GA 970A UD3(p) would be ample. It's stable enough for overclocking.
Remember if you're looking at overclocking you'll need an aftermarket cooler also, a CM Hyper 212 EVO is suitable for a mild overclock, maybe to 4.3GHz.
As for the power supply, Seasonic, Corsair, XFX all make good ones. Make sure to get at least 80+ bronze and preferrably 550W+.