Which graphics card to replace GeForce 8800 GT?

Here is my current config:

proc: Intel Core 2 Duo (2.13 GHz)
CM: asus P5N32 SLI Premium wifi
CG: GeForce 8800 GTS 320 MB
Memory: 2GB DDR2
advance 480W

I want to change graphics card without changing the rest of my config.
What advice to me?
Note that if the price can be 15,000 it will be well and wants "the best" (everything is relative).
Should I also provide a change of food or other component of my current config after you?
I await your advice and comment!

In option you can get this Graphic card.

8800 GTX
- 9800 GTX
- 9800 GX2

Namely that with a 8800 GTS 512MB I can play in CRISYS graphic maximum, but is limited because it saccade slightly from time to time ... On average it goes very well