What's your video card?
That'll really be the determining factor -- a Rage 128 Pro would be iffy (go for 640x480, low quality), a GF2MX would be ok, and a Radeon or GF3/4 would be totally playable.
I run it on my DP450 with a 32MB Radeon under OS X, and it runs quite smoothly (don't know if it uses both procs, but since the speed difference between X and 9 is so pronounced, as in it's faster on X, it must to some extent).
I know a Radeon is better than a GF2 for B&W because performance under X on my new iMac G4/700 with a GF2 is somewhat worse than the DP450.