Room treatment...what is the goal?

Is the goal to get rid of all echo in the room, or do you actually want to have some room echo. Are you aiming for a flat response? What if your speakers aren't perfectly flat, and have sloped up highs? (which I believe is the case with my B&W 805S speakers) Are you trying to match the anechoic response or at least be somewhat close to it? Also does anyone have the response measurements for the 805S? I can't seem to find them anywhere.

I just treated my room with the help of an acoustical engineer, and while everything sounds great, the highs almost seem too dull now on my 805S. They used to be too bright before treatment, but now they seem like they have lost a little of their sparkle and presence. Everything else sounds 10x better though