So far, there aren't a whole lot of G5-compatible video cards (not that there are many G4-compatible video cards either
). In order of how fast they are...
1) GeForce FX5200 64 MB (shipped with old G5s)
2) GeForce FX5200 Ultra 64 MB (shipping with new G5s)
3) Radeon 9600 Pro 64 MB (shipped with old G5s)
4) Radeon 9600XT 128 MB (shipping with new G5s)
5) Radeon 9800 Pro 128 MB (shipped with old G5s)
6) Radeon 9800 Pro special edition 256 MB (available as a retail card)
7) Radeon 9800XT 256 MB (shipping with new G5s)
8) GeForce 6800 Ultra 256 MB (shipping with new G5s)
Normally, the Radeon 9800 SE is the slowest version of the 9800, and generally loathed among PC guys. They'd rather have the 9600XT. But in this case, the "special edition" merely refers to the 256 MB version available as a retail card to G5 owners. If you want to buy a brand new card through retail channels, that is your only option, and it's an expensive one. However, if you're looking for one under $300, there's a slight chance of an older, 128 MB Radeon 9800 Pro surfacing somewhere for maybe a little under $300, and there's also the 128 MB 9600XT that is shipping with the new machines. You might be able to find one or two of those on eBay, eventually, but don't expect them to be available for a very low price. My advice would be to either bite the bullet and go for a higher end card that might just exceed your price range, or wait a while and THEN look on eBay. Prices may go down a bit in the next few months as more video cards from the newer G5s get put up for sale.
Oh yeah, and the Radeon 7000 is basically a gussied-up Rage 128. Total crap, but at least it's cheap.