There is another way to do it. I don't remember the details but I think you use a combination of GraphEdit and Intervideo WinDVD (a version that decodes DTS).

The WinDVD components can be used as part of the graph, decoding the stream to a 6 channel WAV (I think). This method requires a soundcard capable of playing out 5.1 (like the Creative card I have which can play out of 3 stereo jacks), otherwise WinDVD won't decode to 6 channels.

Edit: you also might need the DTSWAV filter from here: http://hypercube.is.dreaming.org/

Like I said I can't remember the details, but hopefully this has given you a few hints (or a few more Google keywords).

DE