The problem with HD4850 Stock Cooler is twofold : Card , Case .

Card : any replacement that lowers temps should translate to better OC because cooling the sensor and no the mosfets means nothing. you get the idea .

Case : heating up the case ( if indeed it does ! I doubt it produces THAT much heat , rather accumulation due to weak cooler) .

The best thing would be a 2 slot cooler .

I am planning on watercooling , but waitqhope for some better stock ( or else I'll pay for this cooler by reducing price at selling time)