Two 8800GTS cards in SLI would generally be faster, but it's an old card so it's not getting any driver love. Get the newer GTS 250 instead. Basically the same card, but nVidia is still supporting it ^_^. Two GTS 250s will prove pretty fast. If you don't need that much power right now though then getting a GTX 260 and then adding another one latter on would be a smarter move.