Also, you should consider the 2500k instead of the 2400, especially with a Z68 motherboard. Otherwise save the cash with the 2400 and get an H67 motherboard, since you won't really be able to OC anyway. Unless you plan to upgrade down the road, I guess.
6870's usually don't run real hot, but I have 2 of them and one I can only overclock about 3% and has no voltage control to push for more. Good cards and great value all the same though, just no headroom as matto said.