Don't buy the GT or GTX right now. NVidia just announced that they'll be putting out an 512MB version which is also clocked considerably higher than the current GTX.
Ergo, wait for the 512 to come out (November 14th), the price for GT or (more likely) GTX will plummet. If you buy it now, you feel cheated in a couple of weeks.
http://www.theinquirer.org/?article=27443