When I bought my 7800GTs, the 7800GTX 512MB was $750, and the X1800 XT was not the relatively cheap card it is now. Both the X1900 and 7900 series cards were not available and weren't even spoken of.As you can see, most of the people on these boards are not SLI fans for all situations... there are good reasons for that.
Nearly every game you'll play, 7900GTs will outperform the X1900 XTX and the 7900GTX.
x1900xtx will crush a 7900gt sli
sli will only bring it`s power when playing high resolution
One 7900GTX - SLi and Crossfire is over rated. But that's my Marvin the Paranoid Android opinion.
SLI/Crossfire makes sense if you use two mid range cards to get close to one top end cards performance. But if you can have more than enough performance in one gcard, then why go the dual high power way? It consumes space, generates unique heat problems etc.