Thanks for your comments. Actually tomorrow they will finally bring all the panels. It is going to be very similar as pictures already posted. I asked 2 acoustic companies to provide me solution and both of them offer the same idea:
difusor behind amp
basstrap in corners
absorbers in side
As i mentioned before i was very please when the home demo. The sound was even better than in the dealer showroom (they do not have any special treatment).
I want to post now here some pictures of the new position of the speakers (SF O3). Before i put them following recommendation from SF mannual (around 70 cm from rear wall) but now i changed to 140 cm from rear wall and the sound has improved a lot. I dont have that dramatic bass problem as before.
Now the speakers are 140 cm from rear wall and around 660 cm from the front wall (behind chair).
About difusor location... i am not an expert... both companies suggested this and i have seen many beautiful setups on internet with difusors behind the music system.
About curtains i know it would be better to follow your recommendation.. but i really dont want to mess that much with the decoration of the house
In few days i will post the final result.