Read Tom's Hardware Guide for a better idea of what to go for. You can provide all the dogma for one card or another (the old ATI vs Nvidia battle) but THG prefer sheer performance to do the talking. I assume you want AGP graphics cards, but if you look to the left of the page below, there are links to PCI-E graphics cards too, if you have the cash and want to upgrade your machine.
http://graphics.tomshardware.com/gra...004/index.html