Btw I managed to rip the multichannel mixes of Once and preserve them. The Siren didn't sound as stupid with the live downmixing. The mix overall though was really different. It's obviously not just spread across the 5.1 system from stereo or anything but the guy doing it might actually have started from scratch.
Did you use the DVD software for ripping and foobar2000 for downmixing?