I have a similar rig.
AMD FX-8320
Gigabyte GA-990FXA-UD3 AMD 990
AMD MSI 6870
Cooler Master 212EVO
600W Power Supply
The FX-8320 is a beast. Mine is overclocked to 4.4ghz with temperatures 25C idle, 55C load. I haven't had any major issues with it. I will need to get a new gpu soon.
The 600 watt power supply is more than enough. I run 3 HDD, 1 SSD, LEDs, and multiple fans with no issues.
I play modern games high-ultra with 2xAA @1080p60