If you do any sort of searching on these forums all you'll find is people asking why they can't get a decent overclock out of this board. I don't know why, but I do know that you can get a better overclock out of board half the price - the P5N-E SLi. Unless you're running twin 8800GTX's at 2560x2048 the two 8x sots on the cheaper board are as fast as the two 16x slots on the expensive board.
If you do want 2 16x slots then buy the EVGA 680i as they are the only ones who've put any development into it and their board now clocks quad-cores whereas the others don't.
If you don't need SLi then there are plenty of better boards;
Abit AB9-QuadGT
ASUS P5B Deluxe
ASUS Commando
DFI i965S-Dark
Gigabyte DS3P
An E6600 should pretty much do 3GHz on stock volts, most will do 3.2-3.4GHz and, if you've got the cooling and the right motherboard, then 3.6Ghz is not unknown, but it is uncommon.
My cooler recommendation would be the Thermalright Ultra-120 with an Arctic Cooling 1225 or 120mm Acoustifan fan set to 7V on it.
