Invest in a modern 3D card with as much memory as possible, it helps to offload the CPU and the AGP bus and future games will run fast.
The market of graphics cards is very fast and high end models become mid range in a few months... there's little point in paying lots of bucks for a card with no support that will cost half the price in 9 months. I would choose the card with best support instead of buying one that is not supported. For example I wouldn't buy a Radeon9700 when there's no 3D support for slower radeons.
I would stick with my Voodoo3 (which has 3D acceleration) until stable 3D drivers for Radeon see the light.
But I agree with you in your main point, getting a good card will help a lot to improve performance.
