Unfortunately you can't play sound from the Apple TV to the A.E., But you can stream music from your computer to the Apple Tv and the A.E. at the same time using the multiple speaker functionality in iTunes. When it comes to Video, iTunes will not allow you to use the multiple speaker functionality for the sound, it will only let you stream the video+sound to an Apple TV. The Apple TV actually doesn't even allow you to choose the A.E. as an output source. So what I do myself is this, my plasma has an 3.5mm headphone out jack and I just use my kick ass computer speakers with my TV. If your TV has the same jack and your stereo has a AUX in, you can just buy an Auxiliary cable. OR, if your stereo supports optical audio you can just buy an optical cable and connect that to your Apple TV. Hope this helps