Speaker Pairing - First Watt F8

Entering into 2024 with a mid-term (12 month ) plan to add a set of new speakers to my system.  I have the time to do the research and as geography permits to listen to a narrowed down list of choices - would like to consider three finalists.  

My system consists of the First Watt F8, Modwright LS 100 preamp, Aurender N200, Schitt Yggy LIM, ClearAudio Concept with MCRU power supply & AT- ART9XI cartridge and Modwright PH 9.0 phono stage.  Speakers are the Zu DW6 Supreme.  I plan on repurposing these speakers to a separate system.  I find the Zu's to be easy to listen to and a sound that I would describe as warm, clean and able to punch.  I would like to take it up a notch and have a more detailed speaker thats in line with my other components.  

Listen to mainly jazz, female vocals ( think Melody Gardot, Madeline Peyroux, etc), R&B and Indie. Large room thats a combination great room/ kitchen/bar  thats 23' by 27' with 10 ft ceilings. Furniture, rugs, island etc with the speakers on a back wall and 12' apart.  

In an article by Herb Reichert in Stereophile, Herb asked Nelson Pass what speakers could most effectively be driven by the F8.  Nelson goes on to say the F8 excels with efficient speakers ( 90 db & above ) that have good dynamics and an impedance above 8 ohms.  The article also has Herb stating that in his experience choosing a speaker with high impedance and a benign phase characteristic is more important than high sensitivity.   Maybe someone can help me out with what is meant by "benign phase characteristic" ? 

Lastly, budget is in the neighborhood of $7.5K and certainly would entertain lightly used preowned speakers.  On my beginning list to further research at this time are the Zu Soul 6, Living Voice Avatar 4, Devore O 93 and Volti Razz.  

Net is that I would really appreciate your thoughts on the above.  Thanks in advance!