Just installed these panels from ATS Acoustics. Boy did things improve. All the slap echo I had with the front and back wall is completely gone.
A couple years back I used Auralex foam in my old apartment but these work much better and look nicer. Each panel runs less than 30.00 from ATS and the build quality is very impressive. They also have several other patterns to choose from as well as solid colors.
Hope this helps with people on the fence with purchasing treatments. It can be done on the cheap. The sound differences are substantial.