@ChaosLord
Well, in PowerMac G4 and PowerMac G5 you can choose your radeon with 128MB.
Powerbook 5,8 (and 5,9?) also comes with a radeon 9700 / 128MB.
But anyway, MorphOS deals relatively efficiently with video ram, so even with 32MB, you can have a big 32bit hd resolution without slowdown and open as many screens/windows as you like. You just have to disable enhanced display (composition system) in this case. Of course, 3d apps requiring big amounts of video ram are another matter (but i can only think of blender, ufo ai and torcs/speed dreams here).