The differences between the two layers is detectable but subtle. On an SACD player expect to hear a bit more of that slam and a better sense of air and space around the instruments. Everything also is a bit more laid back and smooth. While smooth and slam sound like mutually exclusive options on SACD they are not.
I want to stress that these are minor differences between the SACD version and the CD are subtle. Everything I said about the sound of the SACD is true about the CD, just not as true. With the CD you give up the air and space but still get the slam and impact. I'm listening to the second disc of the set as I write this and I don't feel cheated that it is only on a pair of tiny speakers on my JVC mini system. And I say that as a confirmed sound snob.
Like the Stones? Buy these re-issues. They are way better than your present CDs. You don't need a SACD player to benefit from them. They are identifiable by their packaging. They are using the cardboard type cases and have stickers that proclaim they are remastered. I know, I hate those cardboard sleeves too. I remember when Sting issued The Soul Cages in one and it was a bad idea way back then. That cover looks like crap now and unlike a broken jewel case I can't fix it.
These discs will rock you now and if SACD technology catches on you'll eventually end up with a SACD player and you'll get the chance to re-experience them all over again. Isn't that the way great music and great technology should be?