I have recently bought a AV receiver and a AppleTV. I would like to stream music from my iTunes to my AV receiver. Currently, all my files are in MP3 format. Is there any software (preferably open source) that can upscale stereo MP3 to 5.1 (or even 7.1) channel audio formats? I know I can set my amp to take in stereo and play it as 5.1 simulated, but I would like to create original source itself as 5.1 audio. What formats support 5.1 (or 7.1). I think AAC supports it, but am not sure? Also, does iTunes 10 play 5.1/ 7.1 audio