TBH sli is just not worth it. Most games dont support it well. Most games that do support it dont optimise for it well. A bigger cpu and single gpu is just about always better. SLI is mainly appealing to extremists or those looking for a cheap upgrade.
If you do SLI then 2 8800gts are key for performance per $$$ atm.
TBH though a top end Nvidia is will yeild you far less problems and 99% of the time its about the same money when you take into account the cost of the MB, PSU, cooling and everything else. Taking sli out of the picture realy equals a much smoother machine overall compared to the variables with it. Consider as well noise.
Okay bro sli is out, lets build one then, the above unit was built verbatim by you guys and your advise, I know the case is still good, and maybe the power supply, hd and dvd. Mb, vid card, cpu and memory I guess is left.