FST251,

I also did my initial positioning of my TRefs using a bass mode diagram, which worked fairly well but never completely solved the bass room mode problem. Later I experimented with moving the speakers an inch at a time and found I could improve imaging. So as in all things, there are tradeoffs.

Your approach is good, and when you're done with absorbers and diffusers and fine tuning speaker position, you can clean up much (but never all) of what's left using DSP. And that, in my mind, is the correct order. Do the best you can before using DSP.

Good luck!

Charlie