8800 GT FTW. Also, I'm running 64-bit Vista and haven't had any problems. The only games you lose performance on are really old ones, because the 64-bit drivers are optimized to run newer games, not older ones. Even with the performance hit on old games, they'll run so fast anyway that you won't care.
Any 64-bit program that runs on XP should run on Vista. The only programs you lose compatibility with are 16-bit programs from the Windows 3.1 era (and some early Windows 95/98 programs).
In before the onslaught of Vista haters...