For my Nvidia card (a GTX 260) I generally just try to get the most recent drivers that are not beta. People on message boards always get excited about the newest betas but I always find they are glitchy or make games unplayable.
With my 8800 GT I found the best driver under XP was the 178.24, some of the 18x.xx drivers would cause errors and freezes. With Vista the 8800 GT doesn't seem as picky about the newer drivers and I use the latest non-beta driver.
My 8800GTS/320Mb ran best on the NVIDIA Optimized Driver 1.16369, but as you are getting a new one, it'll probably run fine with 185.85.
(Got me a GTX260, trying it out currently, not sure yet whether I'll keep it...)
I highly recomend doing a clean driver install though, so uninstall the drivers and use a driver cleaner if needed to get rid of every last bid of the old ones, than reboot the system with out the nvidia drivers, let Vista set its own drivers and reboot again, than install 185.85 drivers.