Bass Traps

Not much feedback on the base traps, other than wow! Somebody’s getting serious about their sound system. Nice 😊 
Just one question why Rockwall and not Owens Corning 703 rigid panel? Just my opinion, but a 2’ x 4’ panel looks better than a 2 1/2’ x 2 1/2 ft.² square on the walls also why black there are different colors of Gilford’s of Maine fabric that you could use. Also, let’s not forget about the Helmholtz diffusers. 

I have no experience with the Synergistic Research Black Box but I wonder what it actually does and, afaik, it has never been measured.  I own a pair of the  PSI AUDIO AVAA C214 and I've measured them as well as heard what they do. See: Stereophile Review.  Price-y but they work.

Of course, physical treatments generally preferred (and I do use them) but they can be bulky and aesthetically unacceptable.

I read the PSI AUDIO AVAA C214 Stereophile review as well. I love the adjustability which seems much better than a passive.  Pricey.

So I just read this article.  The author suggests that improvement is subtle and it's best to treat the room properly before adding the PSI?

So I just read this article. 

Which article?  My Stereophile article?  If so, I think you drew the wrong conclusion.  What the C214 does is specific to the bass and will not affect anything else.  That means only that it is not a comprehensive solution to room acoustics.

But what is?