depending what res can ya monitor handle ? if you do not intend to game at eg 1600 x 1200 SLI is really not worth it , even so 2 gts models cost a lot more than a GTX. So you better go with one powerfull card and leave SLI or even Crossfire alone... It's a nice feature SLI but I think it's more a show off then a real gaming necessity....

If you do most of your gaming at 1280 x 1024 one powerfull card is the way to go ....