OK, this is the bugger I want... AMD Athlon 64 X2 3800+ Manchester 2.0GHz 2 x 512KB L2 Cache Socket 939 Dual Core Processor
Sure. That's state-of-the-art 2005 equipment... it should be nicely inexpensive!
Actually the AM2 CPUs cost a bit less than 939 (as they are mostly in stock).
So make sure you also get only DDR support, and AGP 8x is a must for a proper older build...