Looking for the next level in imaging...

IMHO omnidirectional speakers present a wide, deep sound stage but smear imaging.  Vivid Giya series is my recommendation.  Others I have heard are Borrensen, KEF Blades, Raidho, and Wilson.  My experience is also electronics play a critical part.  I did not realize the full potential of my Vivids sound staging and imaging until I upgraded from Krell to Burmester.  Eye opening.  Also power conditioning made a significant improvement in realizing the full potential.  Finally, follow the well written recommendations from @audiokinesis and @mikelavigne - gentlemen, well said.  

Kef Blade is a very solid choice for imaging at the price point. It is not critical to be in the sweet spot although it does that well also.

My Opus 3, Test Record 1 - Depth of Image, assists in speaker placement for greatest effect.  The 16 tracks describe what you should be hearing and where.  It's amazing (to me) how deep and wide the soundstage can be.  Then I am disappointed at the vast majority of recordings that showcase very little of this.  Leading me to believe 90% of the soundstage is in the recording and 10% is system dependent.  It is my opinion that throwing a lot of money at new equipment will not change that.   

I agree with what others have said about omnidirectional speakers. I recently heard a pair of German  Physiks and can’t say I was impressed, very clean, airy, sound BUT absolutely no imaging. Everything sounded like it was all blended in together. All high end electronics in the chain.  For $36,000, I was not impressed.