It's not a good idea to get 2 graphic cards at a time for SLI. Best to SLI (or CF) when the graphic card can't handle the most demanding game out there anymore...say around 6 months or more. Gamers with lots of moolah can change anytime they want. I don't know why it is important for them to brag about having the best of the best hardware available. Maybe it makes them proud...

I game and do lots of graphical work on my comp, but I only upgrade when there's significant changes, say about 2 generations ahead (GF6 to GF8, etc.)