Good question Rex, this room wasn't a new construction this is how we found it, I picked this room specifically to see what can be done and help me build my setup knowledge. Having to deal with a less than ideal space is a real world scenario for a lot of audiophiles so better learn how to deal with it. With proper one can negate even the most horrible spaces like this particular room. You can ask
@PeterA who spent a good number of hours in this room and that even a normal conversation was a disgusting experience in there, yet setting up a large horn speaker was quite doable without any room improvements when you know what you're doing. That's fine with a free standing speaker but you can't negate the room when dealing with a corner horn or anything that works with room boundaries then you might have to make physical changes to the space for this type of speaker and typical acoustic treatments aren't going to fix the problem.
david
PS- I don't like or recommend anything like Quietrock, IME it will always over dampen the room!