IMO, SACD is the best format out there for a digital source. HDCD, XRCD, DVD-A can come close, but no cigar. The difference between SACD and redbook can make your rig sound like you got a new one, depending on the setup itself.
Of course with all formats, there will be recording limitations and mixing errors that the format cannot help or erase, so keep that in mind.
Also, the Oppo you had mentioned is known more for video and not sonic qualities. A dedicated SACD player will yield the absolute best sound that SACD can offer. Most inexpensive SACD/CD players and universal players down mix the SACD (DSD) signal to PCM, which will not allow you to really hear what SACD is all about.
I wrote down the differences of what I heard the very day that I got SACD running in my rig. These are my observances.....
Better representation of musical accuracy concerning no overponderance of bass.
Improved separation of instruments.
More dimension / depth of soundstage.
I "felt" [as well as heard] the musical frequencies more at the same listening level.
Better "crispness" to the music.
Discovered new noises of guitar plucks / slides.
Quiter background while music played.
Lead singer was more "in your face".
It sounded as if the amplifiers were producing the music with no effort / less work.