In my case, the "CD" port on my receiver is coaxial (phono jack), so I have added an optical-to-coax converter between my Airport Express and the receiver. In iTunes, I select that which I wish to hear and play it as one normally would, with the Airport Express as the selected speaker. My receiver interprets the bit stream and automatically switches to the appropriate mode: DTS or stereo (for regulars MP3s, AACs, AIFFs, etc), thus I can have a playlist that is a mix of music formats. I have now retired my 200-disk CD jukebox.
When (if?) Apple adds the ability for DVD Player to output the DTS audio stream (or the Dolby Digital 5.1 audio stream) through AirTunes, an Airport Extreme- and DVD Player-equipped Mac could then become an integral component of a home theatre systm. With the Mac co-located with the projector (DVI interconnection) at the rear of the room, and the sound component (receiver) at the front (or elsewhere), Airport Express/AirTunes would tie the two together. Of course iTunes, in that same Mac, would house the audio collection.

