Please visit page 2 of my thread "Snoopdog's Inaugural Bake-Off" and you will see photos of last Saturday's Wammers gathering at my home.
I have been a user of Acustica Applicata DAAD room tuning devices for the past thirteen years. I have four DAAD 4's, six DAAD 3's and four DAAD 2's in my listening room. I have also owned GIK panels (Monster Bass Trap + 4 x Diffusion panels + 4 x corner bass traps), but sold these, back in 2015.
A DAAD 3, on top of a DAAD 4 placed in each room corner, does attenuate bass boom and a "tower" of two DAAD 3's, placed centrally, between the speakers, along the front wall, does help to solidify the centre image. DAAD 2's placed along the side walls at the first and second reflection points, assist with the overall stereo image and soundstage, as perceived at the listening position.
They are expensive, yes! But, they are fairly lightweight, easily portable, aesthetically pleasing and they work!
My experience with the GIK panels was positive, but their presence in my current listening room, was overkill, hence why I moved them on. They do, however, represent a more economical way of improving conditions in a listening room. Their range has also improved, since I bought them in 2010.
I also have experience with Stillpoints Aperture panels (seen in the photos of my BO), but they are expensive, but do an amazing job). I placed them at the first reflection points along the side walls.
By taming the room, you will appreciate the full potential of your investment in hifi, so for me, they are an essential purchase!