Just a note:
Games do NOT benefit from dual cpu's unless SPECIFICALLY written for such a rig. Quake 3, I believe is the ONLY PC game that has SMP (single-multi processor) support.
Game-wise, my system can easily be smoked by a single 2.66ghz Pentium 4, with a 800mhz bus, and faster memory speed of a PC3200.
Xeon's are NOT designed for realtime application efficiency such as games. They are used to enhance server tasks and render crunching (video editing, 3d rendering, and effects rendering). So don't try to race me on that department unless you got a faster Xeon.