Tanaquil, be sure to use system 6 with a machine that's NOT compatible with HD floppies. The SWIM chip can cause damage to 400k floppies, even when write protection is enabled. (i destroyed a copy of system 3.2 because of it!)
So anything until Mac SE w/ 800k drive included is preferred.
Ole, thank you for the recap! I didn't know DC6.3 was also good for CDs