Here are a few:
Acoustical Treatments Master Thread
Freaking long article by Ethan Winer
Real Traps Product Data
GIK Acoustics Primer
Well, I think you should also consider listener positioning and speaker positioning in that setup.
How much are you willing to impinge on your space? I think the speakers, especially the left, will LOVE you for pulling them away from boundaries. You want your ears further from that back wall as well.
You should then ask yourself, are you willing to move both speakers and couch for those critical listening sessions? If you do, you can mark places on the floor perhaps, very subtly, so that you know where the ideal positionings are.
In my experiences, these things will add up to huge effect. You are most likely going to have a very heavy left soundstage. You will probably want treatment on the left wall, as well as the left-front corner, and maybe/possibly the front wall.
You might also want treatments on the rear wall, especially the closer you end up with your head to it. Avoid smearing of audio. When that reflection arrives that quickly, there are NOT enough milliseconds between this reflection and the direct audio from the speakers, to distinguish between them. If the reflection is far enough, or delayed enough, then it will be perceived as ambience.
DIY is the most affordable. GIK costs a fraction of Real Traps, depending. I have both now. If you want, I can send you pics of the 242, 244, and Mondo Trap all next to each other. I also have Mini-trap but it would be too much hassle to uninstall/reinstall those, atm.
The Real traps are encased in this metal trapping. The GIK are not "solid" from front to back, but have a natural gap in the back, maybe a couple/few inches.
Good luck man.