The EZ mode high performance option (or whatever it's called) should get you 4.2GHz without breaking a sweat. With very little effort I got mine up to 4.8GHz stable but didn't spot ANY difference in the usual benchmarks or when playing the games that I play, so in the interest of keeping the temperature down in my den I now run at 4.3GHz.
Incidentally, the ASROCK Z68 boards can get this same chip well above 5GHz!
All on the stock cooler?
The CPU was running at 90°C while running Prime95 (peaking at 92°C), so I am not sure I would want to go much higher. EZ Mode set the target to 4.3Ghz but I was not sure that was going to work on the stock cooler so I left it at 4Ghz. It's extremely fast at 4 anyway, I love it. I'm not a serious overclocker, so a little bit of free performance is a bonus.
:cheers