I found too much absorption on the side reflection points over-damped the sound. I opted for Vicoustic Wavewood diffuser/absorbers in that area, which sounded much more balanced than my thick DIY absorber panels.
That is good to hear! I love your room!
As you say the "Vicoustic Wavewood" is not the same as absorbing panels when they reflect more of the higher freqencies sound on most of the area.
I look at your pictures. And that mat is great for just that. To tweek how much "over-damped" sound we like to have or not.
As we know the floor mat does nothing for the first reflection point on the floor but it acts as a thin absorber that it what it exactly is.. So it absorb only the high frequencies (she the link on the subject that I posted earlier)
So if you experience "over-damped" then out with the mat. If it is to lively in with the mat. :)
Another observation is that low bass is radiating omnidirectional so those low frequencies are radiated behind the speakers. I see great corner bass absorbers. But there is also thin foam that will not help against that the bass is reflecting from those surfaces. Instead those foam will only take hi frequency reflections and also contribute towards "over-damped" feeling. Maybe remove or replace with thicker absorbers.
Is those cool white 3d diffusers the "styrofoam" or other material?
(I never had any experience of them and it is great to hear that they work in that material in that case)