how's the geforce GTX 550 for gaming?
or the GTX 460?
oooor the GTS 450?
The GTS 450 is a mainline, medium level gaming card for medium setting, with some set to high, medium resolutions, and high frame rates. You can juggle those to have high image quality with medium frame rates, and medium resolution, or high resolution with medium frame rates and medium image quality.
The GTX 550 is the updated version of that card, and nVIDIA seems to think it is now much better, thus the promotion from "GTS" to "GTX". The fact is, I haven't heard anything about it, nor have I seen any reviews for it. I will guess it's still in the Mainline Medium class, however.
The GTX 460 is either at the top of the Mainline bracket, or the bottom of the High End class, depending on how you look at it. It should be able to run high image quality settings and high frame rates at medium resolutions, or high image quality and high resolution, at medium frame rates. All three should run Skyrim well enough, with the 460 running it best, and the GTS running it less good than the other two.