All SACDs have a stereo "area" (SACDs have two "areas" on the SACD layer - a stereo and optional multi-channel area). Only more recent releases have multi-channel sound anyway. In my discussions on line, many SACD buyers have no interest in multi-channel. In fact, many of Sony's flagship players do not even have multi-channel playback.
Note: Most SACD players with multi-channel playback capability default to that. You will probably have to hook the player up to a TV to go through the set-up screens to force the player to always play back the stereo sector. It should be a one-time thing. DVD-Audio is another story (for another thread).
As for whether you will hear an improvement over "redbook" CD, I can almost guarantee it. I have yet to meet anyone who's heard SACD and said, "That sounds worse than CD". There are some SACD titles that can show less improvement over the CD counterpart but in my experience, those are few.
I have said it before and I'll say it again: There is no simpler audio upgrade to most listeners than adding an SACD player. You get high-end audio cheaper than buying a super-expensive CD player with audiophile CDs. It's too bad the format didn't take off. Releasese have slowed to a trickle... but I keep buying all that I can afford.
Kevin