saw your zip as 13215, that's where i used to live, thought i'd help you out(well i would've either way).
i would grab a pair of headphones, that you know to work, and try them out.
also plug the speakers in and go to the sound system prefs panel, and crank up the sound. see if you get anything.
also do your external speakers work under OS9?
this is a pretty wacky problem i must say.
gl.