At first glance: If you start adding 5.1 sounds, they should be in a separate directory, and you need to modify index.theme accordingly. See http://0pointer.de/public/sound-theme-spec.html
I also think you need to ship both the 5.1 and the stereo version, so I guess this is also a CD space question.
Other than that, I like the idea. It's almost as good as my idea of having the current release's animal roar/meow as login sound ;-)