There were plenty of multichannel music discussions back when the major labels were still issuing new SACD and DVD-A titles.

I'm pretty much on the same page as Feanor on this topic. The advantage of multichannel music is in how it stabilizes the imaging and conveys spatial aspects that simply cannot be done with two speakers.

I decided to buy a SACD player because of the SF Symphony's Mahler series. I bought the first couple of releases and thought that they sounded so good in two-channel that I had to try them out in 5.1. Those recordings were originally done using DSD, and I frequently go to Davies Symphony Hall for concerts.

I can tell you that for the Mahler series in particular, the 5.1 mix gives you that "you are there" sensation far more effectively than the excellent two-channel mix does. Since I go to Davies Hall, I know how the orchestra actually sounds in that space. The 5.1 mix captures how the sound comes off the stage at Davies Hall. It's not always pretty, since Davies Hall's acoustics leave a lot to be desired, but it's an accurate representation of the live experience.

By comparison, the two-channel mix might actually be a "prettier" sounding mix. But, that's more of a caricatured version of what the real hall sounds like. I can see how some people would prefer the two-channel mix, but it's a less accurate representation of the live event.

With other mixes, it really varies. Many 5.1 mixes significantly improve upon the two-channel mixes, while others are more gimmicky and/or sound worse. Among the mixes that I like, Concord Jazz's 5.1 SACD mixes are incredible in how much they not only use the extra channels, but in how much they clean up the original recordings.

With many of Concord Jazz's two-channel mixes, the engineers used a heavy application of processing to create the phantom center effect. On the new 5.1 mixes, the engineers went back to the original multitrack tape, and remixed it without much of the processing. The result is a much cleaner sound, with greater fidelity and differentiation between the different sound elements.