Interesting question. With the DPS plugin running under Windows I would thought it needs a double conversion to work under Airplay through a music application. For example, my music player (Foobar 2000) has it’s audio output mixed through DPS plugin so I hear through the headphone jack. To make it work with the Apple TV, I would assume that Foobar 2000 would to implement the Airplay feature – which I don’t think it’s going to happen.
I haven’t tried it with iTunes 11. It might be interesting if the DPS plug-in works only with iTunes + Apple TV. Will have to get an ATV to try this out.