Buy a Tbred B or 2500 barton, decent cooler and run it at 2.2-2.3ghz. My 2100xp is running as fast as a 3200 (if not faster). I would never spend over 200 on a processor when a £50 one will perform just as fast!
2100xp @ 2.24ghz
2x512mb 3200
ATI 9700 pro