Benjamin Sun of Gamepyre takes a look at the XFX nForce 790i Ultra SLI and XFX 9800GX2 video cards

The nForce 790i Ultra SLI seems to be an ok update to the nForce 780i chipset, adding true PCI Express Generation 2 capability to NVIDIA motherboards for the first time, DDR3 support and native support for FSB 1600MHz Intel CPUs. From a performance perspective this board disappoints as it only edges the nForce 780i by a small percentage in most of the motherboard tests we tried with it with one or two tests being slower than the 780i motherboard. If you want the fastest most powerful single card graphics platform at the moment it is the 9800GX2. NVIDIA has not approved Quad SLI tests as of yet and it'll be an interesting comparison to see how it fares against the ATI 3870X2 Quadfire solutions. In any event, read the reviews on the web look at all the data before making a purchasing decision and spend your money wisely as I always say,
don't just take my word for it.

XFX nForce 790i Ultra SLI and XFX 9800GX2 Review