Speakers least affected by room acoustics

Our family room is a 20'x20'x20' cube that opens to the kitchen area with some windows near the corners. I have my Martin Logan Aerius i speakers along one of the 20' walls about 13' apart and the listening couch is about 12' away and the floor is covered with a large area rug on hardwood. Contrary to my expectation, I have no echo and the overall sound is very good. Interestingly, the large distance between the speakers to some extent makes up for the inherently narrow sweet spot of these speakers. You need carpet on the floor and the furniture typically does the rest.

Headphones?

Something very directional like Magnepans would decrease the echo but they have a smaller sweet spot.  Any conventional box speaker will have the echo.  Something with a small midrange will have more even dispersion so the echo should be less objectionable.

Don’t compromise.  Look up Vicoustic Flat Panel and Cinema Round absorption products.  Gorgeous looking and very effective.  Oh, and relatively inexpensive for the performance benefit you get not only for sound, but as a living space as well.  If your room is that bad, I guarantee the panels will maks the room more relaxing and less stressful to be in, even if on subconscious level

Using the Cinema Round 2x2 panels in an arrangement like they show on the web site looks like high end wall art in person.  Keep in mind, the images they show on the site have dorky lights behind them.  Having them flush with the wall looks much better.

A heavy rug on the floor would work wonders