Re: nVidia SLi
I answered you.
SLI basically means you can have two identical graphics cards working together to double the performance of your graphics.
But the cards have to be identical, and support SLI. Your best bets are the 6600GT, the 6800GT or Ultra, or the 7800 series.
Only the GT models and upwards support SLI - that's why I've put it in bold.
Master of common sense. If you don't like it, stop reading.