Not for objectivists, thanks.
Today was at a friend's place, we tried this tweak which was huuuge, and he said this is the best sound he has had in his room.
All we did is take a pair of the shun mook wooden blocks you see in the picture below (three shun mooks discs on each block, this is part of their product line, not DIY) and placed it facing the listener, just inside the line of each speaker. There were two Krell monos just inside the line of the speakers, as shown below, and we placed them on top of the Krell. First we placed them at the front of the amp, then moved them back to the end of the amp, facing the same direction. Both the changes resulted in a huge shift in soundstage. Moving them to the back of the amp was massive increase in the stage of the orchestra. Simple and cheap.