it depends on how long you gonna OC your computer, check the temp frequently...cooler master X6 look nice but performance still considerable good, if casing allowed, get a noctua NHD-14...almost the same performance as Corsair H80 closed liquid cooling system...invest a good thermal paste also matter...dun get a rm5 white coloured thermal paste, it dries out in hours after applied...kena tipu one time...

larger the cooler fin area the better the heat dissipation...but turn out a bigger cooler, NHD-14 is the example, almost burst my casing...