rudolfjie

depend on your budget. I personally not recommend Water cooling, cos it always come in high price, and the performance is similar to air-cool heat sink (for same price range), unless you get the high-end water cooling system.

I'll recommend Xigmatek s1283 dark knight, cheap and also with H.D.T (Heat-pipe Direct Touch). If got money, then go for Thermalright Silver Arrow. But no need spend too much money on heat sink, cos i7 won't generate too much heat, you probably won't exceed 70C @4.5Ghz OC (full load)

Hope this will help