Speakers least affected by room acoustics

A heavy rug on the floor would work wonders

I don't think there is a speaker on this planet that is not affected by room acoustics in some fashion.

Sounds like a problem at higher frequencies. Apart from listening in near field, there is only one solution and that is to dampen the reflections.

There are frameless paintable acoustic panels out there that can be adhered flat to the wall surface. They blend in pretty good. And in your case, put high up above normal sightline / above normal decor and wall art, high up in the corners will help with echo... I’m searching for these again myself. I know there out there... 

@recordchanger2018 The guy who designed the Emerald speakers moved on and founded Spatial Audio, which is his current company.  Check them out over on Audio Circle.