Also keep in mind the games have to be written to work in SLI....not every game is just automatically able to utilize both cards
Just to make sure no one confuse. A old game will still work in a SLI setup BUT you will get no advantage from the secound video card. It will be like you only using one card.
I also doubt anyone would spend the money on SLI if they was playing older games like that. Most people buying SLI are the people wanting to play doom 3 and game like it on 1600X1200 8XA 16AF high quility. You will definally see a improvement in doom 3 and games like it if you playing on those settings.
SLI is only for the extreme gamers. If you not then SLI really a waste of money for you and better off with one card.