New graphics card

Right now, I have an 8600 GT, with a P4 3.4HT. I was going to do some upgrading, so I put my graphics card on craigslist a while back, and someone has now offered to buy it. So I was wondering, will a new graphics card help much at 1440x900? By new graphics card, my options are the 8800GT 256, either of the 3850's, and the 3870. Now, I game, but not extensively. I will be buying upcoming games, but my biggest concern right now it TF2, which I believe the ATi cards do better in than the nVidias. Also, I think I can manage the 3850 on my current PSU but I would have to buy a new one for the other cards. So what I asking is, which card would you recommend, and a PSU to go with it, and would that make much of a difference in games with my processor.

if ur mobo can handle them

to yo

I spent some time looking at the charts. The CPU charts tell me that on Prey 10x7, with AA/AF my processor can get 55 FPS with a GTX, meaning that my CPU is bottlenecking any card that can achieve higher than 55 FPS. Then checking the GPU charts of the Prey THG demo, on which a GTX gets 122 FPS, 4 higher than on the CPU charts (using the same processor), so thus, any card on the GPU chart for Prey THG that gets higher than ~55 FPS will be bottlenecked by my CPU (at least in terms of Prey). Is this correct? If so, can the HD 3850, that gets 71 FPS in 10x7, but 52 in 1280x1024, run around 50 FPS with my processor in 1280x1024?

3850 should do really well at that resolution.