Hopefully this is not thread hi-jacking

I have an Asus P5W DH board which has 2x16x PCI-e slots. When I built the computer, I bought an X1900XT 256MB card, and I am for the most part very happy with it. I enjoy CS:S, so I would like to have decent performance, but I have to agree that Nvidia works better on Linux. My question is this: How difficult would it be if I decided to keep my ATI for the main card and used my 2nd slot ONLY for Linux? It would be easy to disable the Nvidia 2nd slot card in Windows, but I'm not sure how I would go about setting up the Xorg config file. Anyone tried this or see a problem with it?