Um... 2d does not put much stress on GPU's anymore. Your biggest concern should be ensuring you can run 4 monitors off the PC. Pretty much any decent graphics card will do. Essentially you've got two choices, get two graphics cards or look at the Matrox M9140 which is designed for applications like yours. The limiting factor is that it is unlikely to do 3D very well, but it doesn't sound like that will matter.