i wouldnt even bother with closed loop in the first place. low quality radiators and low quality pumps just wont cut it. id grab a good heatsink like the noctua nh-d14 or the phanteks equivalent if you are looking for asthetics
if you have to get a closed loop cooler, get the swiftech h220 thats coming out by the end of the month. uses a pump 5x stronger than the ones on these asetek rebrands, copper fins vs the cheaper aluminum fins, and a much btter block
http://www.swiftech.com/h220.aspx