SACD on paper is superior to redbook in that it has more future "potential", but presently the best "Redbook" cd players sound just as good or better than SACD players. In all reality its a proven fact that redbook cd's have still yet to come to their sonic limitations. And there is becoming more and more concensus among scientists that our ears would not be able to tell the difference between a redbook cd and an SACD or other format under identical conditions.
WHen people claim to "hear" differences in SACD or redbook cd's what they are hearing is actual differences in the actual studio recording process, not the quality or upsampling of the cd itself. But if the sound engineer puts as much time and effort in making a good recording on a CD as he would for an SACD, noone would be able to tell the difference. People with SACD players want to believe they have a superior product, but thats nowhere near the case at all. I worked for the Tweeter store that had the official unveiling of Sony's SACD player in Burlington Ma. back in 1999/2000. Sony's original statement SACD player on hand setup in our "high end" room with a pair of speakers with those "super tweeter's" on top, a pair of monoblocks and some straightwire IC's and cabling in which people were raving about the retail cost of the whole setup(around $90,000 is what they stated), but after listening to that setup for a few hours before the guests were to arrive, I can say how big a dissapointment it was. It was unanimous that everyone in the store liked the basic Adcom GFA5802/GFP750/GCD750 with the pair of Amati Homages so much better. It just goes to show that the source isnt necessarily an improvement, and in many cases since that day, I can say its not even as good. At this point I think that its a 100% complete waste of money, andits going to be quite a few more years before I probably end up changing my mind.