The cooler you pick depends on the case, motherboard and the number of ram dimms you have in your dimm-slots. If you've got a moderately spacious mid-tower case with a standard ATX board, you shold be fine as long as you dont use the dimm-slot thats right next to the processor.
Since you have just 2 dimms, and will be placing them in the alternate slots further apart from the processor, You're all set for any basic 120mm width and 160mm tall cpu air cooler.
May i suggest the CM 212 Evo, its got One fan and is 120(l)x80(w)x159(h).
Heres a link: http://www.newegg.com/Product/Product.aspx?Item=N82E16835103099