Fairly sure the patch/hack is still working with recent driver revisions, though I haven't messed with it myself in a month or two. No official support yet of course -- likely never will be.
I'd say go with a used GTX 260 or 250. One of the more recent revision cards, for power saving reasons. Failing that, probably a 9600 GT.
using my old 8800gts works a treat in Batman AA, sure any 8800gt or 9800gt would do the trick, probably find a second hand one close to $50 - $60 range