Keep an eye on the voltage, the auto setting will lost likely over compensate.
Look into setting the cpu voltage your self. You shouldn't run into any problems at 4ghz however.
I have my FX-4100 clocked @ 4.2 it seems stable, I'm just worried about my PSU. It's a Corsair CX500 and I'm also running an overclocked HD 6850 with it. I think the minimum requirements is 500w. Do you think its safe to have the CPU at that speed on daily basis with the little power supply I have? I also have to set my voltage in the bios to 1.425 to keep it stable, but i've read around and alot of the same owners can easily go up to 4.4 mhz @ 1.3v... maybe my PSU isn't strong enough?