Ok. The minimum specs show 1.6 Ghz. To get most games to run well you need 2 Ghz. Some really intensive games such as Soul Caliber require even more. It all depends on what kind of P4 you get.
as long as you got everything to back it up. stuff like:
800mhz fsb on your mobo AND your p4
8x AGP gfx card (not a cheap one, radeon 9600 or 9800 are good)
512MB DDR RAM or more running at 400mhz or higher
etc...
anyway, there's not much point setting up a high-end p4 if you aren't going to back it up with high-end stuff like this. it only takes 1 dodgy piece of hardware to create a bottleneck, and when you are paying for a p4 3.0ghz that's like shooting yourself in the foot.