ROOM DAMPING - CHOOSING THE CORRECT SUPPLIERS AND MATERIALS

I am at the point where room damping is a real issue.  My listening set up, by necessity, is the "room acoustics from hell" 15' X 55' with the front LR speakers placed facing the 15' and 12' ceiling.  Wood floors no carpet (dogs), All walls covered in drywall.  
The B&W 702 S2's are notoriously bright - in my experience, that is also true. 

Anthony Grimani (YouTube/Audioholics ) recommends 15 - 20% room coverage with alternating damping -diffusion panels.  SonitusUSA is out of stock on the panels that dampen the higher frequencies.  
I need to get the harshness / brightness under control as well.

Here is my Question: Which manufacturers should I be looking at for sound damping and sound diffusion panels?  


Building and improving my gear as I go (current hardware below):
AVR 7.2 / 2 channel music setup:
Denon AVR3700H (105 watts)
Rotel 1590 2 channel power amp connected through the Denon pre outs.  
Bowers & Wilkins 702 S2 (left right) speakers.  
Bowers & Wilkins 802 LCR (center power connection by Denon amp)  
Paradigm Phantom V1 LR Side
Paradigm Atom V1 LR Rear
SVS PB-1000 - YAMAHA YST-SW315 powered subwoofers
Sony 85" TV 

Lumin U1 Streamer
Denafrips Pontus DAC (R2R)