If you don't need SLI, then you don't need to bother buying a board with it. Unless you plan on strapping a pair of 7900GT's together, why do it? You only get ~50 percent more performance (overall) with SLI, so why spend twice the money on an expensive card, when at the point of paying 500 dollars for a pair of GTO's you could have just spent 400-450 on a Radeon X1950XTX that is the fastest single-GPU card on the market today.
If the board you want happens to have SLI, that's great and it could be useful if you wanted to prolong the life of your current performance level a bit longer before an upgrade.
I just hope you're not hung up on it, though.