I tried and tried. I saved the file as AIFF and AIFC, but they still wouldn't show up in preferences. reboot. copied the files to all the directories. No dice.
the .aiff extension was what was missing.
THANKS.
If you haven't resolved this yet, I have a simple solution that just worked for me.
Go to netinfo.
Click the lock to make changes.
From the Domain Menu select Security.
Select "Enable Root User".
You should be prompted for a password and then asked to verify.