i've never used a 600 celeron, but personaly i wouldnt recommend it, a p3 1ghz would be perfect. if you've got a agp slot, look on tigerdirect.com they carry some of the older radeon video cards (7000 series, n such) pretty cheap.
As far as choosing a Proccesor,
THIS IMAGE IS FROM TOM'S HARDWARE. THIS IS NOT MINE. 300 hundred hours of testing went into this, by the people at TOMSHARDWARE.com !