....its only a slight increse in performance, but for some real gamer itll make a diffrence and give you that edge.
That's the thing about SLI or Crossfire that I disagree with the most! For the 'real gamer' it makes no difference whatsoever, because the performance difference is beyond that point where it makes any difference at all to frame rates and respinsiveness in actual gameplay. Instead, it's at the point where the only detectable difference lies in benchmark tests of the hardware.
I once saw a games journalist describe the concept of the ungamer - the person who maintains a high performance games system, but for whom the hardware itself is the passion in his or her activity, rather than the games. It is the ungamer for whom small differences in SLI or Crossfire performance is meaningful.
The 'real gamer', as implied in your comment, can maximise games performance with a single, high-end display card. The person playing at a competitive level where small differences in hardware performance will give an 'edge' in currently available games is not going to be worried about a difference which is not going to have an impact until the hardware becomes outdated.