Room Response

I have taken years and a lot of experimentation in trying to make my listening room, as good as I can. I have incorporated absorption and am currently making a quadratic diffuser for my front wall. Even though I've done or doing these things, my room isn't perfectly balanced, as far as it's layout. It's a basic triangle 19'x21'x9'. I'm concerned that my TT rack on one side, my end table on the other etc, is disrupting my sound. My listening "triangle" is pristine, but know all room contents has an effect. In your experiences, how has your room floor standing contents, etc, effected your sound? Im mindful about diffusion and absorption.  I find I may have to adjust my balance control, depending on the CD, or LP. I experience this on a regular basis. I think this is normal though. I may be TOO analytical. I have gone from a 3 seater couch, to single listening chair,which has had more of an effect than I thought. Guests have to take turns in the sweet spot. Couldn't occupy thee same spot anyway.  Unless she's my wife:).