I know MoFi has some checkered history but their I Robot and Los Lobos KIKO Original Master SACDs are worthy upgrades over CD quality. Absolutely agree Red Book CD can sound as good or better than SACD versions on many titles. Those master tapes are key.
Remastered CDs, HDCDs, SACDs
CD is my only source. My album collection is somewhere around 800 discs. I have found significant differences in SQ (sound quality) comparing original releases to remastered releases. To my ear, Bob Ludwig was the best engineer for that.
I was speaking with a local recording engineer and mentioned how much I liked Bob's work. He replied Bob boosted 2 dB at 150 Hz.
In order of SQ (worst to best) my rankings are original CD, original HDCD, remastered CD, remastered HDCD, original SACD, remastered SACD.
Those rankings are usually the case, though occasionally they may vary.
Happy listening to all. Enjoy the music!