The Corsair H50 and H70 are just rebranded Asetec 550LC and 570LC. And the Asetec 510LC is the previous version of the Asetec 550LC. Asetec doesn't sell their parts for retail but only as OEM tho, so you can only buy the Corsair-branded versions, if you're not a OEM. So the question is actually down to Corsair H50, Corsair H70 or CoolIT. Going by the reviews, the CoolIT has some issues with a rattling pump, so you're down to either the Corsair H50 or H70, which are both excellent and only differ in the size of the radiator and therefore performance. If you're not interested in overclocking your CPU, then the H50 will be sufficient enough with the single fan attached to it.