Ok guys

The name is scaf, underscore doubleohseven scaf-

Wow.. ok guys, from the sound of so many EXPERT opinions, do you think I should remove the top cover of my SACD and any/all my bluray players?

Removing the cover from my Aronov tube integrated was an improvement. The only way to know if it will be better or worse with your players is to try it and see.

From a few opinions, it sounds like if I let all my redbook CDs lie out in the open they should sound more open. Maybe that would work just as well with all my cassette tapes! And going one step further, I bet all my recorded VHS tapes should be stored in direct sunlight! I would hate to know what would happen to them all if they were to stay under optimum operational temperature for more than a few minutes, let alone for more than a decade..

Way to ruin an otherwise good question.

I have a Denon 59L and Pioneer PL-518 and play both with covers on and down. Guess my ears aren't very good because I've never been able to hear the difference with cover up, down, on or off.
I have a small listening room. I guess that could have something to do with it.

Scaf, first of all, if you listen to cassette tapes, you shouldn’t be here. But yes; leave them uncovered.

Dust cover on or down when NOT playing, up or off during playback. This is what I was taught by the "old-timers" when I was young. The dustcover can exaggerate or amplify microphonics. Turn your system on. select the phono input (do not actually play the record). Leave the tonearm cued in the "up" position. put the dustcover on or down. Gently tap on the dustcover and plinth. Repeat the tapping with the dustcover "up" or off. With most tables and cartridges you should hear a significant difference.

I've seen low mass arms so attracted by static from the dustcover that they are lifted right off the record!  Stands to reason that less static can also attract the arm, even if not enough for full lift-off.  So I NEVER play with the cover down.  Of course, I've has a Well Tempered TT/TA since 1987, whose dustcover is not hinged, so is set aside during playback. FWIW, the oil damped spindle and acrylic platter seems to attract dust and static a lot less than any other turntable I had before...including Duals, HK Rabco, Linn, SOTA, Technics, etc.