I understand that you could combine the matrox cards g450, g550 and g200 and you would need just one driver - their universal driver available at their website. I currently have a g450 and a g200 driving 3 samsung dvi panels using the universal driver with no problem. Got both cards from Ebay cheap.
I have three monitors with the following system: A: Matrox G-450 card purchased in 2001. It is a dual monitor card. B: My Compaq Presario 6000 (recently purchased P4) has an imbedded video card. The combination here of the Matrox G-450 and the imbedded video card allow me to operate three monitors; and I can drag a mouse across all three as well as drag and enlarge software windows across all three monitors. I have no complaints and it works adequately. Hope this helps.