I have a FX-8120 overclocked to 4GHz currently. CPU voltage is at 1.38125 with 260MHz on the CPU Bus and a 15.5 CPU ratio. I'm currently using the Antec H2O 620 I won from here. I've yet to run a stress test for the 4GHz overlcok but I've run Prime95 for 3.5GHz. The CPU cores were at 58C max at the time during load.