I'm looking at buying a new gaming PC on which to do some XNA development. Before I buy a machine with SLI graphic cards, does anyone know if XNA has any problems taking advantage of a SLI setup?
The only consideration you need to make with XNA is the shader profile you code to ... that is, if you write custom shaders at all :-) aside from that, as long as the video card is dx9+ compatible, you should usually be fine.
Edit: According to the list of Supported Operating Systems and Hardware for XNA Game Studio 3.1
To run XNA Framework games on a computer running a Windows operating system, you need a graphics card that supports, at a minimum, Shader Model 1.1, and DirectX 9.0c. We recommend using a graphics card that supports Shader Model 2.0 because some samples and starter kits may require it.
Furthermore, according to NVidia's marketing material, the following cards are SLI, and support up to shader model 3.0