If you are in the market for a new video card, I have to highly recommend the GeForce 6800GT. It’s not a decision you will regret any time soon.
In my opinion, it’s entirely not necessary to go for a 6800Ultra unless you just have money to burn. The GT can be overclocked very easily right out of the box to match the Ultra, and it costs $100 less.
It does run a little hot though, so make sure you have a well-ventilated case.