Bryce does not support the AltiVec in G4, neither, so you will probably notice a little or none speed improvement if you get a G4. With a G3, you can still get out more power if you overclock the processor, which should be easily done - as for myself, I did not do it, because it seems silly to me ;) but if you dare, check up the xlr8yourmac.com site and go for it. The G3 processors are all slow-jumpered unless you already have the fastest one.