Front wall treatment

Assuming your speakers radiate forwards then anything thicker than about 4 inches will be worthwhile for broadband bass absorption. I would not bother with midrange or treble as nothing much over 600 Hz goes backwards behind the speakers so anything thinner is not likely to have much effect.

I spent several weeks talking to and studing panels from GIK, ATS and acoustimac.com. I finally bought quite a few from acoustimac.com.

They are VERY nice and well made. You can order one at a time, (unlike GIK that requires a minimum of 3) and are a little cheaper.

I am VERY HAPPY with my purchase.

I've had very good success with the use of curtains. Not too heavy. Not too thin. Going with enough fabric to be 1.5 to 3 times the rod length produces enough folds to act as difusion. About two to three inches off the wall are where mine will wind up... again. They'll also hide the ginormous screen that's new too.

The heavy ones in the pics of my rig are now at the rear of the room instead.

I'm adding also some corner Chunks to each side, and some immortal (silk) plants about the speakers too. I'd hope they work out for first reflection points too, so I don't have to make panels as well.

BTW Curtains on that wall will hide other panels, egg crate foam, etc. yet still allow them to be effective.