I would avoid using too large of a chair or sofa. I switched from a small barrel chair to a large arm chair. The arm chair is more comfy, but I noticed a drop in coherence and focus in the soundstage. My room is quite small, however, and the new chair is too large for the space it's in.
looking for a chair
I found a very comfortable chair for my listening room. It is the La-z-boy 354 rocker-recliner. It is roomy and very comfortable but it has a very high back. I don't know if the fabric will absorb or reflect the sound, but I am concerned that the soundstage will be destroyed. Do you think this would kill imaging or make the system sound more forward. I can't borrow it to try but I would be interested in your thoughts or your experiences with high backed chairs in your listening room. thanks