Reading more about it, I was incorrect about the Airport Express. I was thinking it was a more basic form of their Airport router (which in a certain way, it is). However, I hadn't read about setting it up as a remote itunes node. That could possibly help you, but as was mentioned before you'd be limited by controlling it from your base PC or your iphone app connected to it.

I was thinking you wanted to use the wireless music playback portion on your receiver itself, which is where the protected content breakdown for me started.