Definitely diffusors behind you to, well, diffuse back wall reflections. I used two Aurelex diffusors in my former listening space and these really made the back wall recede. And absorption of first reflections to the side walls is a must to reduce phase cancellations. A couple of floor-corner bass traps won't hurt either.
difussor's
I "think" im in need of some sort of diffusing on front wall of small listening room...I would be really interested to hear some experiences of some that have been through it...don't think I need an absorber type...as I have some bass traps in lower corner...just lacking clarity of sound stage...diffusor?