And unfortunately I cannot fit a second in my case because of its size so I need to pick up one of the single slot GPU (I think they are called). I am not sure If what I heard was correct but I do not know much about xfire and I was told that If you have an OC'd gpu it will be bought down to the engine clock of the non OC version. Eg my current card has 890mhz and If my second had 950mhz it would be reverted down to 890hmz.
I was considering a 6950 because I hear they can be unlocked to be as fast as a 6970. Honestly I am not too familiar with gpu unlock or OC so I was just going to pick up a 6970 to avoid the hassle. I was also considering the 6990 to do trifire but $800 is ALOT of money and I will cry myself to sleep if there is a price drop soon on the 6990 and I pay the full price.
Here are some pics I took awhile ago of my case and motherboard to show you if I can fit the other dual slot card: