Looks like I might be able to fix the problem with mod_sound soon. There was a bug in the SDL code for Wii that caused the sound to initialize incorrectly when trying to play an ogg sound... This resulted in a very crappy sound, as described here.
Will report on progress and upload some test code when I get time to test this.
PS: To clarify, the code is really inside the binaries I uploaded a few days ago, I just need to link that code to a newer revision of the SDL code and hopefully, that will give us sound support.