Are you going to install Windows XP 64-bit? If so, I have 4 sticks of DDR2 6400 2GB. Make me an offer.
There are some really nice Core2Quads out there on ebay as billbart mentioned for dirt cheap compared to their retail pricing.
Wonderful project you got going! I have a couple like that sitting around myself. One of the first games I played was MechWarrior2, you guys remember that?
Awesome and frustrating at the same time. Clunky game mechanics, but that was part of the challenge.