This observation is particularly interesting to me:
now I use it EVEN IF THERE IS NO EQ WANTED, as with all the dials on flat, it actually improves soundstaging as compared with without it. I it is also DEAD SILENT noise floor...
Traditional thinking (as far as I know--I’m no expert here and this could be WRONG) is that every extra device in the signal path is detrimental to the sound. So your perception that this improves the sound even when set "flat" is potentially quite significant. It would be interesting to know if other owners have experienced this as well.