Yes, you will need an aftermarket CPU cooler for overclocking. The stock cooler works just fine with the CPU at stock speed. I can't seem to find any images of the inside of that case. Could you either upload a picture or measure from the motherboard to the side panel so we know how much room there is for a cooler? Does it have a fan at the back of the case? If so, do you know what size it is? Another option may be to replace the rear fan with a 120mm liquid cooler if the fan is 120mm.