The main reason I'm still considering an nvidia card now is because that's what I've already got in the rig, so I know what to expect. An ATi card would be an unknown now. Their drivers have always been awful (though they weren't alone in that for many years... their competition simply got their act together and they never did), but the Omega drivers negated that problem effectively when I had a card back then. Who knows now.
Ugh. I can't make decisions anymore.
EDIT - Well, I went with the Sapphire 4850. Overall everything I read said that the 9800s were really just rebranded 8800s, most seemed to run hot, apparently there were extensive driver problems with them (unusual since nVidia is usually the better company there), and the 4850s were really about the same price for significantly better performance and higher room for overclocking, especially due to heat. The one I got seems to have a good fan that keeps things cool, though is a bit loud, and I know for a fact that it works on non-PCIE2.0 slots. So it seemed to be the best deal overall, and the easiest thing to be confident about. And all for under 200 bucks. Amazing.
Thanks for your comments and for being a sounding board, guys. Appreciate it.