T-B, You have enough power. Make sure you have a big enough room for the 20.7s or maybe try the 3.7s with subs. 4 meters wide by 6 meters long for a minimum would be good. The speakers need to be at least 1- 1.5 meters out from the front wall. The distance to side walls is somewhat less critical for dipoles.
As A. Wayne says, most dealers don't set the speakers up well. An over-damped, dead-sounding room with lots of absorption or speakers closer than 1 meter from the front wall takes all the life and dynamics out of the sound. I've rarely heard them sound good in a store either but there probably aren't many dealers in France.
Good luck!