Looking for the next level in imaging...

MBL is a poor choice for your quest.

Look at "concentric driver" designs....TAD, KEF Blade, etc.

Lots of good ideas and suggestions as always.  Keep them coming.  To clarify my vision of image - I have the soundstage-  the presentation of instruments and locations. I’m lacking the 3D, the depth.  I have a little bit but know it can be improved.  The current speakers have been toyed with - toeing in more/less move wider/narrower and all it does is compact or expand the left to right image.  I have treated room and moved treatments around as well. I have also tilted speakers upward and downward everything has given minimal to depth. 

Martin Logan’s do space and purity, but like omni’s are not ideal for organically solid full frequency imaging. one reason is that the mid and lower bass uses dynamic drivers, a different type of driver, so the coherency in the low frequencies is reduced. this detracts from imaging.

a more traditional 2 way dynamic speaker system might be best for this priority. it makes the fewest mistakes.

imaging is about room<->speaker synergy, and room symmetry, combined with surface treatment of reflections. to get imaging that is ’right’ also requires that the room has good bass balance, so images are cohesive, and contain full frequencies.

with your budget, there are any number of quality 2 way speaker systems that can work.

do you have a dedicated room?

is it symmetric? how high is the ceiling? can the ceiling be treated?

windows or screen next to or behind the speaker?

any distortion in your signal path or speaker will restrict imaging by locating the sound coming from the speaker. so eliminating distortion anywhere promotes imaging everywhere since the signal transparency disconnects the sound from the speaker location. you hear less distortion, more of the music signal.

seating position will also be a factor. sitting in the near field and working on toe in and toe out will allow you to optimize imaging. near field means more direct sound, and less reflected sound. an advantage for imaging.

all these factors will effect the potential imaging of your system.

Depending on material, soundstage can be wider and deeper than the room and instruments can be located with accuracy as to their placement.  Sometimes stuff even sounds like it's behind you.

I use my own creation which include JBL 2241H (18"), JBL 1151J (9-1/2") and a modified Great Heil. The crossovers are of course of my own design.

This is an older video with some crossover mods done since, but you can see what we are dealing with. Of course don’t expect a YouTube captured on a Nikon DSLR video to image.

BTW, the other speakers in the room include the modified JBL L200s (with increased cabinet volume, L300 long horns, slot tweeters, revised crossovers), one-off Big Red Supers (Altec 604E2s/Utah aux woofers) triamped with one-off electronic crossover and Marantz power amps), and Chartwell LS3/5As.

Room is 26’ x 16’ x 7.5-16 feet and about 5,000 cu ft.

None of these other speakers soundstage/image like the "Mermans" (so named for Ethel because of her loud and clear voice and disrespect for authority).