Do I need to run an optical audio cable to my AVR in order to take advantage of 5.1 surround with my AppleTV? I noticed on my iTunes purchased content the center channel and two rear channels are not being utilized. Running the latest firmware, and I am able to take advantage of the extra channels using my XBox. Also, I thought the advantage of HDMI was that only one cord was needed to handle all of the information. Any help on this would be greatly appreciated.