Preferably, but it doens't have to be same brand/model. Try to get the same or one with the same clock speeds, mem etc.
Btw, i think i remember a single 6850 is better than 9800 gt sli . . .
Thank you very much I appreciate your help. I think I will just buy two 6850's then and run those SLI.
Err.. the term for AMD is crossfire, not SLI. I think first you should check whether your motherboard support it. And if you're able to buy two 6850, why not go for a single card but higher spec such as 7870 or 7950?
Good point! Realized that myself after thinking about it a bit. Did some research too and buying just one higher spec card is better then two lower specs running simultaneously. Thanks again!
Why buy 2 6850? Couldn't you buy a better single card?