Graphics Card and Display (Help me choose)

I am building my first sweet computer and I wanted some help choosing a graphics card. My set up so far is as follows

Intel i7 920 (will overclock to ~3.8 gHz)
Asus P6T Deluxe MoBo
Apevia X-SniperG-BL Case
6GB (3 x 2GB) DDR3 Corsair Dominator PC3-12800 1600MHz RAM

So I'm looking at nVidia cards, and I'm wondering which card should I get. First question, do any of the nVidia cards support directx 10.1? Also, how does the GeForce 9800 gtx compare to the GeForce GTX 275?

What would work well with my current setup (I don't want to waste money on a card that is limited by my CPU). Please recommend what card you think I should get. Thanks

EDIT: I have been looking at some displays and it appears that they're max resolution is really low even though they are 26" widescreens! 1366 x 768 on a 26"?? I've got a 17" right now and I'm on 1024 x 768, how can this be?

Well the GTX 275 is no doubt better than the 9800GTX...
Stick with the GTX 275 as they are better value than the GTX 285...
For that card, get a 1080p(1920X1080) resolution 21"/22"/23" monitor...