For some comparison, have a look at the released-today (which I probably will get my copy of in the evening
) Tiger.
G3, G4, or G5 with 256 of RAM (512 is probably better), built-in firewire (why, I dunno...), built in or external display (of course....), and 2 gigs of space.
http://www.apple.com/ca/macosx/upgra...uirements.html