Right now I only have a radeon x1550 and I would like to upgrade. My two options are either the msi geforce 8600gt oc 256mb(128 bit gddr3) or the sapphire radeon x1950gt 512mb (256bit gddr3). Which one would give me the best performance in directx 9 games?

Here's the X1950GT vs the 8600GTS (which is better than the GT). You'll see they're fairly comparable in the overall. They go back & forth depending on the test. If you can afford it, go for the X1950Pro instead:

http://www23.tomshardware.com/graph...

Here's the specs for the GTS...see how your GT OC compares for the GPU & memory speeds:

http://www.techpowerup.com/gpudb/19...

Great, thanks

sorry forgot to add. Right now I have dual boot with vista, if I got the geforce 8600 gt how would games in general compare in performance wise in vista to xp?
By the way the games I play most include battlefield 2 and 2142,dods, and company of heroes?

If you have Vista & you're gonna upgrade the video card anyway, you may as well get a card that supports DX10. Have a look at this article:

http://www.tomshardware.com/2007/10...

How much are you willing to spend? Are you in the US? You can get a standard 8600GT for about $80 at newegg. The cheapest 8600GTS is $110 (after $35 rebate).