Looking for the next level in imaging...

Another direction is to get a quality subwoofer.  I just bought a REL S510, and it is an amazing improvement to my two channel system.

Suppose you buy a million dollar system and you don't like the sound.... what do you do then? I've had several systems over the years and it wasn't the most expensive that sounded the best. As for me, Martin Logan speakers sound really good.

I will second the Larsen and KEF suggestions. I have not heard the Larsens, but they are consistently reviewed well. And I have KEF Reference, the concentric design makes for a large sweet spot and very good imaging. 

Two specific ways to increase soundstage depth, as you seek.  First, increasing the distance of your speakers from the front wall can have a huge impact.  If this works in your room, it would be my first move.  Second, consider a tube based amplifier.  My McIntosh C22/MC275 do a much better job with depth than comparable solid state amps. 

Also, are you working with a dealer or other professional?  As noted above, this is a really complex process.  An hour or two from an experienced person might be well worth the expense

As @patrickdowns touched upon briefly with instrument placement I don’t see why so many here look for which instrument is where in a song. Are there more genres than classical orchestras that play music in such a way?  Does most everyone here listen only to classical music? Surely it doesn’t matter as much in a studio where everyone is standing? And the sound is in the hands of the engineers anyway. With classical music being a small part of the world of music I fail to see the importance of what instrument is where in a song. I have some classical music in my Qobuz library and it sounds good but I really just want the music I like to listen to to sound great and not worry about what is where. Am I missing something to listen for that would improve my listening experience ? I listen to 60s 70s 80s 90s etc.