If you want to save $, consider the GTX460. After rebate and on sale, I was able to score an EVGA one for $100 even. I can max every setting in Oblivion and get 60 FPS even outdoors (unless there's a lot of CPU load... one core and all.

) I'd consider it a best-bang-for-the-buck. I notice that they don't go on sale much though possibly due to this!
Don't worry about the lower stock GPU and memory clocks... comes with an NVidia utility so you can OC it as simply as dragging a slider and monitor the temp.
Beware the GTX 550 ti!
Edit:
The cards u've shown are good but significantly more expansive. I'm trying to stay < 200$Heh... you posted that while I was writing
"If you want to save $".
Also http://www.gamesas.com/index.php?/topic/1242901-unofficial-will-my-pc-run-skyrim-discussion-34/page__st__40__p__18871122__hl__tech__fromsearch__1#entry18871122 or whatever one succeeds it.