[Consortium] Processing Tivo audio

I have a Tivo and I wish to play the AC3 5.1 output (spdif/toslink) through my computer (KXStudio) and sound card (Xonar D2). The sound card has a spdif/toslink input (I can play digital stereo from a cd that I input into the toslink using VLC). I need to know how to convert the digital AC3 from the Tivo to a 6 channel digital wav streams and send those streams to the sound card. If possible I am looking for an example from someone who has done this processing or part of this processing before. Otherwise, I am looking for suggestions for the best way to implement this. Can I only use alsa or gstreamer or a combination of the two or ffmpeg or something else. I am not sure where to start. I am trying to turn my HTPC into a surround sound preamp. XBMC can handle playing video files. VLC can handle (in addition to files) cd's, dvd's, and bluray's. In think I can handle analog inputs (turntable and tapes) since the data streams are not encoded, but I don't know what to do about AC3 from the Tivo.