There's a firmware update for the A05 on their site (1.33?), but I think you need to boot into OS 9 to use it (ie, not Classic, the real deal).
I have a flashed Radeon 8500 and installed an A05 in my Sawtooth, with no problems other than the laser in the A05 dying after only 3 months and some non-heavy use. Thanks goodness they have a 1 year warranty.