if you're only going for 2.8, you may not even need to bump your voltage, in which case your heat increase will be minimal if at all. You can squeeze very mild OCs out of stock coolers, so long as you monitor temps and be very conservative with voltages, as this is the biggest factor to adding heat to the CPU. I second the recommendation of an aftermarket cooler though. Cooler temps never hurt anything, overclocking or not.