In reading your post it certainly seems that your system is very complicated and would benefit some from a simpler setup. I am not sure why you would want to add all the other devices to complicate the HDMI chain since it is already a pretty fragile invention and sometimes doesn't like to play across multiple devices in a system. The more devices in the video path the worse the A/V sync issues become. I, like you, have a lot of older equipment that sometimes doesn't support all the newer gizmos out there and have to either accept the limits or change out some parts. At this point I have decided to stay with 1080P vice 4k and will wait until there is a driving need for the object based audio gizmos.

As for the parametric EQ on the 976, it appears to be much more adjustable than anything I have seen on most AV Processors and will allow you to customize you system to sound the way you want using REW.