First, welcome to the forums!
Second, you need to provide some additional info here. Are you building new? Have you picked out your cpu? Which one? We don't even know whether to suggest an AMD or Intel board from what you posted.
Third, SLI is generally only recommended if you plan to do it now. Don't plan to buy a second "sometime later" when prices fall because by the time you get around to it there will be a single card out that will eat an older SLI rig without burping.
Fourth, what resolution do you intend to use for gaming? Follow this guide to choose a card best suited to your needs.
1280x1024 and lower: 8800GS ($110)
1600x1200: 9600GT ($130) or 8800GT ($170)
1920x1200: 8800GTS 512MB ($200) or 9800GTX ($300)
2560x1600: 9800GX2
This is rough and there is some overlap (8800GTS may be needed for 16x12 in some games for smooth play for example) but this is pretty much what you should consider before buying your card. In general, don't spend more than you need today because tomorrow something better/faster/cooler will be available.