Xeons are designed for server use in mind. They are not really designed to aim at the games market as the P4 or duos are. To be honest the money your intending to spend on a xeon processor would be better spend on a top of the range core duo. However the xeon processors use a different socket thus would not fit the way you intend. Im not sure if I am reading this right but you do have one huge block of text.
The xeon workstations are designed for 3d CAD video or graphic manipulation rather than gaming.