With an Athlon XP-M, you can get it up to a near high performing chip if you know what you're doing. I highly recommend it.
edit - you'll need to dish out some money for good some decent RAM or you may find it difficult to overclock very high.
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w