It really depends on what you want to use. The Radeon 7000 was their budget card and would be somewhere around the current GeForce 4MX. The 8500 was a better card and would be better than your GeForce 3.
Currently the budget processor is the 9000 series with the 9500 as a step up and the 9700 a step above that. I don't know if any of these are supported driver wise.
As for the other manufacturers, they still use the ATI processor chip so they should be just as effective as the one built by ATI.
