In OS X Mountain Lion, is there a way I can mirror my (latest gen) iMac video to my AppleTV and the sound to another AirPlay device (i.e. an amplifier)? I would like to create the following setup: A video projector should be mounted to the ceiling together with a connected AppleTV, where the video of my iMac is streamed to wirelessly. The sound should be streamed wirelessly and (halfway) synchronously with the video to an amplifier. If AirPlay can't do this for me, what would be a (halfway) cheap alternative solution?