SACD

I would say that, in my setup, most of the time my SACDs do sound better than the "regular" CD, MQA from Tidal and high-res downloads, but not always.

Most of the time the mastering seems to produce a more "musical" result, but not always.  With just a few of my SACDs I wonder if the mastering engineer ran the CD quality digital files thru some sort of "up converting" algorithm.  I have the latest CD master of the Steely Dan "Aja" album, which IMO sounds significantly better than the SACD.

SACDs sound amazing on my Sony SCD1. So do Redbook CDs. SACD does seem to have more air, detail, and soundstage.
One concern I have is maintenance of the laser assembly for SACD. If I understand correctly, the Redbook section is fixed in position whereas the SACD section requires manual calibration with reference discs and an oscilloscope. No one seems to have these reference discs available. If anyone knows, please share that info.
So where would you find a high-end SACD player to replace what was made back in the day?
I purchased a used SCD-777ES as a backup. The transport assembly required repair to play any disc. It now reads single layer SACDs but will not read SACD layer on a hybrid disc. I am SOL on fixing the laser without proper calibration.
Fortunately, the SCD1 still reads all formats perfectly.