I should also say that if you do grab the Geforce 4 Ti - that isn't a bad card, either. With 128 MB of DDR graphics memory, it should keep you up with the most demanding 3D games. The only downside to this card is that NVIDIA makes sub-par drivers for this card (and other Geforce models) for the Mac, which don't let the user take full-advantage of the card. nVidia has been widly criticzed by Mac users for producing sub-par, if not just completely bad, drivers for their cards. That doesn't mean the card won't perform well, if not excellent, but it won't be performing to its maximum ability.
Also, I should note that I have not verfied that the PC version of the 9800 Pro Radeon card will work in 4X-AGP slot Macs, but I did hear it from someone else (triplezoom). Apparently some guy bought a 1.8 G5 from Apple with the 9600 Pro, and instead wanted the 9800 Pro later on. Apple told him they couldn't sell him the card separatly, but instead told him to buy the PC version of the card and it would work. It turns out the card does work, but only in 4X-AGP slot Macs - not in 8X-AGP Pro slots. Something along those lines.
If that made sense, hopefully I helped.
