A regular store-bought computer is enough. Custom, high-powered computers are only needed for extreme graphics applications, such as editing a motion picture.

Instead of 4 monitors, using 2 wide-screen monitors will work. One screen can display more than one chart if it is large enough.

Dell Precision T3500 Workstation Xeon Quad-Core W3520 Dell T3500 Precision T3500 Workstation


you need to add 1 more video card for 2 more monitors
also 99 buck online upgrade to win 7.

some more deals
https://www.amazon.com/Dell-Precision-T3400-2-33GHz-Business/dp/B002WK45AW