There is a cure!
I did a demo at home with some panels and what a difference! I can live with this sound.
Basically they put Diffusor behind the amp, basstrap on both corners and absorbers on the side.
Now i need to find a solution for absorbers to make them like a stand and customize colors.
I see from your recommendations that you mention to put a panel also in ceiling on top of listener position. I will ask them to do also.
But overall very pleased with the solution from a sound point of view.
Aestethically... well.. i guess i will learn to live with that... if i customize colors and match all of them... they will not look that bad.
First time i play with acoustic treatment.. and it is as you always mention in this Forum... what a difference it makes... like magic.