Hello,i want to change my graphic card to HD6850, do you think i will get 2x performance boost?
And what do you think about combination q9400+hd6850, will processor bottleneck my graphic card?
That cpu should overclock fairly well. At stock clocks 2.6ghz is too slow. If you have a oem board and cant overclock, the hd-6870 or hd-6850 would be a better match. (It doesn't hurt to have more gpu power, it just wont get you any more fps vs. the cheaper card.)
Even though your fps will be about the same with the hd-6870 vs. the hd-6950, the hd-6950 is a better card that is more reusable if you upgrade your board/cpu/mem later on.