Hi, thanks for an interesting discussion.
My hifi equipment is now at such quality level (but by no means exclusive/very expensive) that decent cabling makes a difference. I have just changed all power cords ensuring all are plugged-in correctly phase-wise, and deployed a cheap power filter/conditioner. The difference is audible giving me more punch and holographic sound image.
That said, I have already perfected speaker placement using quite a few different methods. One of the most educational was "The Art of Rational Speaker Placement" found here https://youtu.be/84Pf0ycbyBM. I even contacted the presenter, and bought his written guide.
Since then, I have diverged from this speaker placement, but following his process gave me insight into what is possible with speaker placement. Especially, careful backward-tilting of the speakers mentioned in the end of the video and guide, is the icing on the cake: it opens up the stereo image submerging the listener into the sound.
Maybe, careful tilting could give you the extra depth and height in your stereo image.