how far do you sit from your speakers?

Robert Harley suggests sitting "slightly" farther away from each speaker than the distance between the speakers.

http://www.avguide.com/hifibooks

You could try treating the wall behind you. I suggest panels at least 4" thick. ATS acoustics make cost effective acoustic panels.

My Quatros are a little more than 7' apart and I set a little less than 9' away from each speaker. This is actually what the Audio Perfectionist uses for his Vandersteen 3As, but I started out about 8' away and my Poang chair tends to drift back on the carpet, but the soundstage sounds good at this distance.

I have a few smaller rooms and one larger one. My preference is the larger room where I can sit a good bit back and take things in rather than being more immersed in the sound closer up.

I sit 10 - 12 feet away.
A fluffy (as opposed to hard) blanket on the back wall works wonders.
Also, a chair without a headrest is preferable.