To answer the original question without having to use in room measurements yes acoustic treatments on side walls for early reflections, in corners and on ceilings for slap echo and also diffusers on back wall do make a huge improvement for reducing brightmpness and increasing imaging and overall clarity. You can hear everything way more clearly and focused just using side wall early reflection absorption. I can tell you from experience in my 12 x 13 basement theatre / listening room it was one of the best improvements to sound and coherency I've done. After treating my room I heard instruments, nuances and background vocals I never heard before, everything sounds just more tightened up, better bass and just much better.
You ears tell your more than anything.
You ears tell your more than anything.