I would stick with one of the last three. I would also say that's too much money for a 9800GTX+. The other three choices would serve you well, I'm sure. The only thing I would say is to research the different cooling solutions for the 9800 GX2, if that's the way you go; or even mount a case fan blowing right in between those suckers. I had a 7950GX2, and the top card always wanted to run hot.
I like your choices. Have fun!