I've been working a long time toward reaching SDA imaging nirvana and wanted to share a few hints I've learned along the way that may save others some time.
As I've tweaked and upgraded, my system has become far more revealing. It's now basically to the point where the focus of a specific voice or instrument is essentially holographic. It's position can be heard and visualized by height, direction and and distance from my listening position.
At one point a few months back the center image seemed to be originating from a point left of center, and higher than the height of the tweeters. I started checking connections, balance controls, etc. and found nothing wrong.
I remembered it had been a while since I checked the "alignment" of the front plane of my speakers and found them to be a bit out of whack, and I've even acquired an inexpensive laser level since then to improve accuracy.
I first level the speakers so the are 90 degrees perpendicular to the floor.
I then shoot a laser level beam from the left wall across to the right and get both speakers exactly parallel to the wall and the exactly the same distance from it by nudging the outside edges of each speaker just into the beam.
You can get nearly holographic results with a good source, clean signal path and precise speaker alignment! :)