I have also "yet" a 4870x2, and looking for a better cooler than stock, the problem is that the only one avaiable I know, it's from "Artic Cooling", and btw guys the production is discontinued.
You can have a look here:
http://www.quietpc.com/products/ultragrade/ac-acc-xtreme-4870x2
PurpleStank, are you a complete stupid? ... lol You don't know really nothing about this... -.- omg