Definately go for the Radeon 9800 Non pro. That thing will dominate pretty much anything you throw at it and i think i heard somewhere that if you flash the 9800 non-pro bios to a Pro Bios then you will have a full blown 9800 Pro with 380/680 or whatever clock speeds. Im pretty sure that most people are trying it with the Sapphires and they have had some nice success with it.
One thing though, which 9800 are you looking at, is it the plain old 9800 or is it the 9800SE? If its the SE ive heard some horror stories about it.
A wise monkey never monkies with another monkey's monkey, unless another monkey monkies with another monkey's monkey before the wise monkey monkies with another monkey's monkey.