Quote from gnome:
Unless you have special needs from your software (like perhaps custom indicators or certain Java apps), most trading apps run almost entirely from RAM. Therefore, a fast CPU doesn't make much difference except at boot, shutdown, loading apps... etc. Once everything is loaded, the CPU sits idle mostly, waiting for something to do. (My main, 4-monitor rig with TV tuner runs about 2-10% CPU all day... and that's mostly the TV tuner. My other computer, with 2 trading platforms, runs 0% CPU all day except when executing a trade it'll bump up momemtarily. My Aquarium Screen Saver app runs about 30-40% CPU when on a secondary monitor.)
So, any modern C2D CPU or better, on a rig with adequate RAM (2G likely enough for XP), running on WinXP or x64 is probably all that matters.
Also, be sure your mobo has the proper slots [and enough of them] to run the video cards you want.
The rest is just bells and whistles.
High powered video cards not required.
small edit..
) Someday I'll go ahead and build a monster for the fun of it, but for now the wife would kill me....uhh.. I mean I don't need it. 