I currently have a P2 400mhz, Asus P2/B, 64mb pc100 sdram, and a riva128-based video card (hehe). Pretty much anything I buy will be a substantial leap over this system, so I might go with:
AMD Thunderbird 1.4ghz
Epox 8k7a+
256mb Crucial PC2100 DDR SDRAM
Kryo2 (maybe ultra...I don't play...