Relax guys, the war is over!
Great news ! I can't believe this ! I took Geof's info to heart about The Cube (he has the next model up the line- Cube SE) being very sensitive to RF and placement and last night I was moving it around a lot. Finally I placed it in front of the other equipment (a place where I would'n consider placing anything) and far away from all the cables in the back and... The Cube became DEAD QUIET! Because of the lack of any floor noise everything improved, detail, articulation, bass and treble extension, soundstage, you name it.
After a simple location change I was finally able to find out what The Black cube is all about.
Can you believe it?
Now, my next tread will be about a new turntable, which should be friendlier and more relaxed since it's about sound and not that much about technical issues.
Thank you all and stay safe!
Emil