This made very interesting reading.
My room is not as sophisticated as yours mike - however after moving recently I have managed to create a dedicated room in my house. I was very pleased with the overall sound with some major structural alterations and some acoustic treatment.
But, as we do, could it be better? - after reading various internet info (in particular http://realtraps.com was very useful) I have built some large bass traps for the walls beside the speakers. This immediately improved the already good imaging and bass definition.
Similar to yourself I went on to build two ceiling traps to reduce reflections and placed rugs in front of the speakers. This has made further improvements to imaging and detail.
Reducing reflections, especially primary ones, seems to be a relatively simple means to making significant improvements to the quality of the sound one hears. I know much has been written over the years about the most influential component in the system is the room, my recent experience has borne this out.
The combined effect of this DIY work has made a huge improvement - it has not over dampened or deadened the room - clarity, detail and sense of space have been the winners.
