Older matrox cards (ebay) load the system a lot more than modern cards. Lots of cards do work (I like nvidia based cards but probably for no really good reason) and the key is to stick with the family to avoid conflicts when you add extra cards. See the other threads.
Nvidia does indeed make the best multi monitor cards now. My next system will probably incorporate Nvidia. No hurry though. I run my computers until they become hopelessly outdated. BTW, I haven't noticed my old Matrox use much system resources at all. CPU is usally running at at about 15% capacity while running the three programs that I run each day. No worries.
I used to really like AMD but now I am very dissapointed. My room in college gets really hot in the summer, and believe it or not my CPU is overheating constantly. I hope to go back to intel as soon as possible.
Intel is eating AMD's lunch right now. The C2D platform gives the best bang for the buck. The AMD x2 AM2 is a dead end platform. Compare CPU here: http://www23.tomshardware.com/cpu.html?modelx=33&model1=430&model2=464&chart=171