as always, next year will have something MUCH faster, looks like AGP is gonna die and PCI express bus will rule, the next gen Nvidia cards (see link) are seriously overpowered as well (well...until we get hold of them

), as a rule of thumb...get the highest number card you can afford with 128mb of ram (eg 5200-5400-5600-5800-5900 etc), ATI cards are supposed to be good as well, you might like to look at those also, by this time next year it will be out of date anyway

, just be aware that if you have a agp mobo that isn`t 8x then you will be wasting cash buying the top end cards, they need 8x to get the throughput, you will just choke them with a slower port.
http://www.pcformat.co.uk/reviews/default.asp?pagetypeid=2&articleid=29785&subsectionid=679&subsubsectionid=711
Mentor.
PC1: P4 hyperthreading 3ghz, 1gig mem, 2x160gig hd`s, Nvidia FX5900 gfx, 6 way surround sound, PC2: AMD 1.2ghz, 512mb ram, FX5200 ultra gfx, stereo 16 bit soundblaster, ups.