OSX may say it runs with 256, but believe me you will chew up your hard drive with caching and virtual memory.
OSX is built upon the cache idea of do it once, remember and Ill do it 10x faster next time. So the more physical RAM the better, always.
Apple giving you only 256 is a slap in the face cuz 512 is BARE MINIMUM and to be realistic, if you can afford it 1GB is the min i recommend for any G4 or G5 (and a G5, 2GB min if u got dual processors, like meeee)
If u aint mac dont bother but check out www.macobserver.com and www.macrumors.com for specials and deals.