I have my D2 speaker cables and my D2 phono cable connected to the powerbox. For both cables, the powerbox noticeably lowers noise floor. Music feels & sounds louder but isn’t!
When A/B comparing the speaker cables, the bottom end is tighter and deeper with the powerbox in the signal path. My Stenheim speakers tends to come to live at higher volumes - the powerbox lowers the threshold of that level.
Hope this helps...