Yes that's a sick system and they overclock like crazy. You will destroy and then burn the q6600 performance up and then thank yourself for getting the 2500K. Check this below, and this is stock only:
AnandTech - Bench - CPU
I would also however recommend a decent cpu cooler if you are going to be overclocking it, other than stock cooler, which I happen to be selling cheap, Titan Fenrir!
Titan Fenrir and Skalli CPU Coolers Review