I bought the Sony X85K.
I did all the settings, trying everything we've talked about, and while it was wonderous to have all of that screen real estate and I got it looking almost bearable (as in so so close to 'good'), in the end I still got low levels of eye strain, so I took it back.
The underlying problem is that I cannot get a good clean setup on my PC - meaning I cannot be sure of what was being sent to the Sony TV. After foolishly updating graphics drivers a while back it seems something broke permanently in my setup and I cannot get back to my old good setup or create a new one. I suspect something low level has changed in my hardware - that not even GPU or mobo BIOS reflashing seems to be able to fix.
So… the battle continues.
Note - I didn't try the X77L display that this thread was originally about. Maybe it works better… but here in NZ there's little ability to return things to the store used. I went for the X85K as it had better latency figures.