I forgot to mention, in case anyone else cares to try this, that once I made the BIOS settings, the optical drives were ALSO treated as AHCI -- neither of them could be used to boot anymore.
The "fix" that appears to work is to move them to the Jmicron jacks (the white ones on the motherboard). That is still using SATA in IDE mode and, thus, the drives are back to being able to be used for booting.
