Hey guys, I know this is an old thread but...
Try running your ATV to both sources. In my setup I have it running to a Yamaha Rx - V373 via HDMI for movies and tv. I also have the optical output from the ATV running to a Rotel preamplifier, which is connected to a pair of speakers that are great for music.
If I don't want the music to come out of the 5.1 receiver, I simple turn of the 5.1 receiver. Same way for movies, I will turn off the Rotel amp so the sound only comes out of the receiver.
By doing this you will take advantage of whichever component you need when you need it, reaping the advantages that it provides.
And Peachtree stuff is highly thought of in many audio circles. Very affordable for what it can provide. Can sometimes be found a little cheaters in eBay so try their first.