Is AMD officially supporting the 4850X2 with driver updates yet, or are you still at the mercy of Sapphire to provide updates? If the latter is the case, I would put a big yield sign on buying a 4850X2. Along with the horror stories about its fan and lack of control, custom drivers and lack of user-defined profiles mean you're always going to be getting the short-end of the stick with updates. Given this part is only made and supported by one partner to begin with, I'd bet it'll be the first CF part to fall out of support as well going forward. Is your 4870 1GB being RMA'd? If so, why not just get a 2nd card for CF, as your board supports CF at x8 PCIE 2.0.