As crumb said, the fastest you'll probably find is an MDD Power Mac G4 (uses DDR RAM; I read that the G4 doesn't have a DDR-capable bus, but that's still faster than PC133 SDRAM) plus one of the third-party accelerator cards (which go up to 2GHz.) Those, however, can be pretty pricy. You may find it cheaper and easier to get one of the 1.67GHz PowerBooks - I haven't tried much in E-UAE on mine, but in other demanding applications (Flash video) I've found it quite a bit snappier than the 1.25GHz G4 machines.