How important is it for you to attain a holographic image?

Boxer12, Often reflective side walls can be conquered by simple, but radical toe of the speakers, with out the need of using ugly treatments on the walls to deaden high frequency reflections. Often, not always. Give it a try if you already haven't. It worked for me. FWIW there are other benefits to this type of speaker set up as well.  

Boxer, leave your speakers alone, they are a very critical adjustment that I'm sure you have fiddled with enough times to have them precisely as they should be. Nothing is worse than messing up what you already have right.

Increased focus of the soundstage means you are close to having what we're after. Stop and evaluate.

I'm sure everyone has fiddled endlessly with speaker placement and toe in until they've gotten a satisfactory left, right and center channel image. This will not change when you are attempting to get "holography".

We are into "The propagation of sound" when we get into this dimension we call holography.
Geoffkait told of some of the professional devices that can be helpful; however, that goes into a whole other realm of study, and expense; I used as much common sense as I could muster along with flat out "luck", and succeeded beyond my wildest dreams.

Once holography is realized, it's like entering another dimension in sound and music; tone and timbre sound closer to the actual instruments, the music on old records sounds like new music.

I didn't change one component or move one speaker; it was all about room improvements in regard to the propagation of sound.

A couple things. The Trial and Error method of speaker placement - move a little, listen a little - or a random or convenient placement can only result in finding local maximums - at best. There is no reason to fiddle endlessly, nor any benefit. Second, the optimum speaker placement changes as the room is treated over a period of time and should be re-evaluated whenever room acoustics changes. Lastly, most people believe that the best holographic soundstage is achieved by placing the speakers relatively far apart and toeing them in toward the listener. Actually that’s not true at all. Generally, most speakers should be placed relatively close to each other, let’s say for argument sake, five feet. With no toe in. My 2 centavos.

I had to think way back when I was a kid and got my first record player. What a piece of crap. I listened to Vivaldi, and some Mozart to start with. At the time, the record player, with built in speaker, was housed in a cabinet with a door on it. I soon learned that the position of the door affected the sound, and thus began my life as an experimenter in acoustics, along with electronics all around me. But my point here is that the musical message was somehow available even through that miserable setup. As time went on, and decades later, I bumped into a holographic image with the system that I had at that time, and never let go of the that ideal for my listening. My present listening room is not ideal however, and I must judiciously adopt placement, treatment while all the time being aware of the WAF.