Wayne:
I am afraid I have to disagree with a portion of your last post. While it may be true generally, I know that it was not true in my particular case.
I ran my home theater system for over a decade using phantom mode and no center channel speaker. I started on a Yamaha in the days of Dolby Prologic and a 1050 for DD 5.1. I attribute this to the superior imaging and sound stage that my old Dahlquist DQ-10's provided. I never had problems being able to isolate the dialog. Almost without regard to seating position, I was still able to point to the speaker. This included mono sound sources like newscasts. My sense is that others with excellent imaging speakers could also achieve the same result.
I would like to point out that when I switched to NHT speakers, I purchased a matching NHT center that pretty much conforms to your recommendations except that I have the center setup horizontally. What I have noticed is an increase in the dynamics and sound intensity by switching but this could easily be a function of the efficiency difference between the DQ-10's and the NHTs and the additional amplification the center is now getting. FWIW I have not noted the lobing but then I wasn't doing critical listening in an off center position. I will try to see if I notice it.
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Living Room 24x18 open 1/2 flight up to a raised dining room/hall 24x12
Outlaw 976 pre-pro running 5.1 system
Outlaw 750 for Artison Masterpiece LCR and 2 NHT SuperZeros rears
Velodyne Servo FX-1200
LG OLED65C8PUA via HDMI2 to/from 976 HDMI ARC
Roku Ultra
Samsung BD-D5500 BluRay
Amazon FireStick 4K to 976 Aux HDMI input for Amazon Music Ultra