As a VERY rough guide, a G3 at 600MHz is about 5-6 times faster than a 603e at 200MHz. But that's not all. Taking away old Amiga bottlenecks and adding a much faster memory bus, as well as eliminating context switches and having a PPC native OS, I'd *estimate* that an A1SE is about 10 times faster than a 200MHz BlizzardPPC board.
An A1XE with G4 at 800MHz could be expected to be 2-3 times faster than that.