SACD a 5.1 medium?

I'm a two-channel dinosaur, and I wonder if SACD has promise for two-channel, or if it's intrinsically a 5.1/7.1/etc. medium. Most of the SACD discs I've seen are labelled "5.1." Do you need a 5.1 setup to get the good sound? If you ran a 5.1 SACD disc through a two-channel setup, will it sound any better than plain-old redbook?

All the multichannel SACDs work fine in two channel, and as far as I'm concerned are a very significant advance over regular CD playback. Upconversion to 24/192 cuts the degree of improvement over CD playback, but not the fact that it is there.
All SACDs have a stereo track. Most are superior to their CD equivalents although that is dependant on the specifics of mastering.
That's reassuring. It leads me to another question. Say a two-channel master is remixed into multiple channels for SACD. In a traditional two-channel setup, all the information from the master would be sent to the two channels. In the remix, all that information goes into multiple channels. If one were to replay that remixed SACD through the front channels only, would some information be lost?
Sure but why would you? I repeat: All SACDs have a stereo track. That means that on a MCH SACD, you would play the stereo track if you do not have a MCH system.

Besides, who needs a stereo master remixed into 5.1 fictitious channels?
Amen. I was worried that remixing would degrade the original stereo image. But if the SACD discs are encoded with two-channel tracks as well, that's not a problem.

One more question. How does SACD improve the sound? In other words, what does the SACD process achieve that makes it superior to redbook? I'm assuming there has to be some improvement; otherwise, there'd be no need for the format.

(Not looking for a flame war here, just information.)
Use google to find the technical differences. Subjective comments can also be found although you may get some right here.
Jverona: The one major difference between CD and SACD is that the sampling rate is much, much higher on SACD. Whether that actually makes a difference in sound is open to question, however. If you search around, you'll find a lot of technical answers to your question; most of these answers will be wrong. The truth is, no one knows for sure how, or even whether SACD as a *technology* makes a difference.

A lot of people think they sound better, of course, but at least part of that has to do with the fact that older recordings are remastered for SACD, and these remasterings are often an improvement over the cruddy initial CD releases. (This problem crops up even on hybrid SACDs, where the CD and SACD layers are mastered differently.) How much of the difference is in the mastering, and how much in the technology? No one can honestly say.

Of course, even if all the difference is the result of better mastering, that's reason enough to get into SACD. When it comes to sound quality, mastering counts for a lot.
Kr4...What makes you think that the Master recording was stereo? The Master is usually a dozen or more channels, so even the 5 channel version is a mixDOWN.

There are a good many SACD available which are not multichannel. In a multichannel SACD the stereo recording is on a completely different area of the disc, so what you get, if you play that area,is a stereo program as the recording engineer chose to mix down from his master.