These posts about overclocking are torturing me, because I've been on vacation for over a week now, and my newly built machine is home collecting dust. Anyway, I would start off going for 2400 mHz, and see what kind of performance boost that gets you. This is what I'm going to go for. Then if i feel that i need it, i'll push it to 2500 mHz, if possible. I don't think I'd try to go further, just because the extra few mHz that might be possible aren't worth the extra risk and possible lessening of the longevity of my system.
I have a similar system to the one you are planning on, so i'll definitly post my results once i attempt an overclock (never tried it before in my life!)