What should i upgrade first?

[Tech cash]

Hi, i just got this computer, it's specs are
Intel pentium 4 3.2Ghz
2Gb 633 mhz ddr2 ram
150gb HDD
Nvidia 8600gt 256mb.

I was going to upgrade the cpu and the graphic card, it can support core 2 duo CPU and i found one that's a E7500 chip with a clock speed is 2.93 ghz that will work with the motherboard, and i also want to upgrade the video card to a 9800gtx or nvidia 200 series, although once i get the first upgrade it will be a while before i can get the other. I want to know which will (Upgrading the CPU or GPU) give me the best performance increase.
I want to play games like crysis warhead and really other high graphic games, which it can do ok already, but i'm getting a high res screen soon screen soon.This is the kind of thing i will be using it for and i'm telling you to give you a better idea of what i want from it.

 

[Trotter]

D. All of the above.

I would boost the graphics card first. Doing so will probably require a new PSU capable of powering the card, though.

Another cheap upgrade would be to replace the RAM with a faster set.

 

[Hefemeister]

Another key factor in your ability to upgrade would be your power supply.

Which one do you have?