Well I know with the SLI motherboard, you're going to need the nVidia card to use SLI. Also, the 7800GTX is much, much more powerful than the X850. In addition the ATI card doesn't support pixel shader 3. Pixel shader 3 is used in a couple of cames now, and it is expected to be used in a number of future games such as UT 2006. Only the nVidia 6000 and 7000 series support pixel shader 3.