I run a Phenom 9850 @ 3.0Ghz with 1.325V without any problems. I've only got a cooler master hyper tx3 for the cooler, temps get around 57C full load. I could overclock higher, but since it's no longer my main computer, I can't see investing in a better cooler for it.
mine is sitting at 3.1GHz right now, was 3Ghz for sometime now. all i had to do was change the cpu multipier from the bios to x15 (for 3Ghz) and to x15.5 (for 3.1Ghz) voltage on auto.
AMD Phenom X4 9950 BE @ 3.1GHz
MSI K9N2 Diamond SLI
Gigabyte G-Power II Pro cooler
my temps are 28C idel and 42C full load prime95 (ambient temps are 20-25C)
as people say each cpu has different overcloking capability so try increasing the multiplier from the bios by 0.5 each time and see if it boots and runs the OS when you reach a point where it doesnt boot or restarts go into the bios reduce the multiplier a little and check for stability.
i would say it can easily do 3Ghz safe and sound with no hassle.