3D graphic. you can consider Dual CPU system. many 3D graphic software support more than 1 cpu.

either AMD or Intel is fine.

example:
Intel system:
Dual Xeon 3.0G 800FSB
Iwill DH800, or Asus Ncch-DL, (overclockerable), tyan, intel, supermicro..
ram, at least 1G.

depends on how much he want to spend.