Get this
heatsink. You'll also need to buy a decent fan.
Here's a review of the heatsink. They OC'd a 2500+ to a 3200+ with this heatsink and a good fan. I'm gonna upgrade my system in a few months and this will be the heatsink I buy. Just don't buy a loud fan and it'll be quiet. If you plan to OC then you'll need a loud fan to keep things cool.