Go for sli pay no attention to others since I can say that first hand. People say this and that but just go with your gut feeling. Two 9800gt in sli hold really well in most games that benefit from sli and crossfire. Just be sure they are clean and you have a good psu. Overclocking them yields a nice boost. If you card isn't as good as the other in overclocking then in riva tuner set the top card to clocks that you know that work and select the section card and set it to clocks that it works best. That is right clocks don't have to be sync.