No way to improve on the excellent post Alex linked to but I hope I can expand on one thing he said. I think it really does depend on the “mix/recording.” Just because something is SACD or DVD-A doesn’t mean it’s always going to sound better.
It seems to me that when stereo SACDs sound better I think it’s mainly when the songs are re-mastered better for the SACD version. A couple examples I found of this are standard CDs of Boston and The Bangles compared to stereo SACDs which sound much better. In both cases the SACDs exhibit much better clarity, imaging. On the other hand comparing a standard CD of “Blondie” to a DVD-A couldn’t tell the difference.
Adding to why I think the mix/recording makes the most difference, is when comparing a U.S. standard CD of “Nena” to a German import standard CD, the German version is vastly superior.
One caveat to my opinion, besides that it’s only my opinion, is that I do all my listening on “detailed, articulate, bright” (call them what you wish) speakers. I can’t see why it still wouldn’t make a difference with more “laid-back” speakers but I have no experience with them.
In the case of standard CD compared to Multi-Channel SACD and DVD-A recordings the multi-channel almost always sounds better to me. Some examples of this are Pink Floyd’s “Dark Side of the Moon” and Vivaldi’s “The Four Seasons” where the SACD and DTS recordings both sound more detailed and enveloping. However, there are even exceptions to here as I found comparing standard and Multi-Channel SACD versions of “Carmina Burana” where I couldn’t tell the difference.
Another place I think Multi-Channel shines is in some live concert recordings. I have one of Roger Waters “The Wall” live in Berlin that sounds like you are right there in the arena.
Also don’t overlook regular DVDs. The DTS track of “Jethro Tull Live at Montreux 2003” sounds way better than my Aqualung CD.
So in my opinion I think that SACD and DVD-A are worth it in some cases especially in Multi-Channel. However, I’m not convinced that stereo SACD versions are necessarily that much better than well mastered standard CDs.
I’ve found links like this helpful before deciding to spend the extra money on an SACD vs CD.
http://www.highfidelityreview.com/reviews/review.asp?reviewnumber=19939611
Cheers,
Dean