I Agree that the ONYX is a great display. They kept it 4k and is calibrated for 500 nit highlights with calibrated black levels.
For 8k signals with 2,000 nits that is a lot of additional bandwidth that has to get to the panels, and the send box is designed for the largest configuration, that is where tradeoffs were made resulting in dithering.
The good walls seem to be in the 4k range at the moment.
Planar promotes the .9 wall at CEDIA as suitable for home theater. They should work with the original poster in adjusting the 0 and 1 nit levels better, or heck crush a bit. The input requires tone mapping and good scaling from a separate vp like lumagen or upcoming envy, if you do not want 3D, 3D on walls at 120 has the most solid negative parallax of all displays.
"I have spoken."