Depending on how much you have to spend and the dimensions of your case I would go with the swiftech 240x. It beats almost every cooler I am pretty sure and also beats everything in noise as well (DBA)
^I recommend air coolers for the AMD chips, as they can put quite a strain on motherboard VRMs. Which motherboard do you have?
Air coolers help the VRMs some, whereas liquid coolers only cool the CPU.