Your Sacd player will not need to down mix anything, all multichannel sacd's also have a two-channel sacd mix. Set your player's default to two channel in it's set-up menu.
Dave got it right, the funny thing is that between the multi-channel and the stereo mastering of the SACD in some cases one version is preffered sonically over the other. You would think that since they were both JUST remastered they would be very similar this is not always the case.
This brings up another query I have about this subject, its clear that SACD is a niche market at best. Most of this niche market is two channel(I know I couldn't afford to do my system multi-channel!), how many audiophiles are using audiophile gear in a multi-channel SACD system? I know amany audiophiles and only know of one who uses high end multi-channel system with an SACD source. After all NOT all SACD's are multi-channel, so of the almost 2000 SACD's available it seems hardly worth the expense, hmmmmmmmm. I think I may have hi-jacked this thread if so I am sorry, this is just my rant for this fine day.
Tireguy...Of course each of us has an opinion of what it takes to be "High End". However, I think the essence of your question is "do you implement a multichannel system with components inferior to those you would choose for stereo?" This same question could be asked at the level of $2000 speakers, or $20,000 speakers. As I, for one, put together a multichannel system, it never occured to me to downgrade quality. The three Maggies in the front are the same models I would buy for stereo, and the rear speakers (which would have been more Maggies if they would fit) are of similar quality and cost. The rears do lack subwoofers, but I have the drivers in a box and may get around to installing them someday. As some may know, I am a strong advocate of having five identical (or at least equal) speakers for multichannel, and I think that much criticism of multichannel results from systems that skimp on the center and rear channels.
Funny, I heard Dark Side of the Moon ("Money") at the C.E.S. I think that it was the Wilson room???? Anyway, it was REAL high quality multi-channel SACD room, and I found the presentation sort of disconcerting. Maybe I'm just an old fart, but DSOTM was permanently etched into my halcyon consciousness as a 2 channel mix in the '70's. As has been commented upon in this thread, finances and spatial considerations make SACD multichannel much less prevalent in the home than SACD stereo, one would think.
I share Fatparrot's concerns, though perhaps not his judgement on muti channel per se. The thing is a high end 5.1 system is not only costly but importantly takes up quite a degree of space and secondly though I am sure when done well Multichannel sounds great, the thing is that a lot of times the mastering is odd: too much infor via the rear channels etc.
As such, for now, for audio only, I am more intent on improving my 2 channel's systems ability
Fatparrot, yes, we are old farts!
In my (our) day we had the music coming at us from all directions, although if I remember correctly, it was mostly drug induced.
For SACD to be trully the pot-o-gold in multichannel music reproduction, a listener must be positioned in the perfect place, in the perfect room and with the perfect acoustic treatment. I have found it easier to "approach" (only) that (perfect) scenario with 2-channel. I wish only the best of wishes to those hardy souls who attempt the former.