Speaker recommendation for married couple

I've had similar discussions with my wife and my wife had similar comments to your wife's. I hope we're not talking about the same wife but since you mentioned you're in Europe, we should be OK on that count since I'm in the US.
Back to speakers. You're wife's observations lead me to draw two conclusions. She like the point source sound of the Kef's and the natural sound of the paper drivers of the Sonus with it's simple crossover. The Kef's do not sound as natural to her because of the metal cone -- never a natural sounding solution. Because of close proximity ceiling surface you will need a consistent off axis response = point source or coaxial design. Or an open baffle. Also, you need paper drivers for natural open sounding vocals, such as paper cone full-rangers.
So...
Look at paper cone coaxials like Tannoy's (go for the 12" models) or Emerald Physics open baffle. They have natural, dynamic sound and are not overly bright. The point source "open baffle" designs will have less problems with ceiling and wall reflections and a natural presentation of semi-omni directivity.
Another option -- full range paper cone based speakers with woofer support like Rethm Bhaava.

Just look around -- paper cone + point source, or 8" full-range with woofer support. 
Herman

See last two posts. We both wrote concurrently and mention low ceiling and good off axis performance -- nothing will beat point source here for off axis uniformity.

One more that fits the bill:
https://www.cambridgeaudio.com/products/speakers/aeromax-2
or
https://www.cambridgeaudio.com/products/speakers/aeromax-6

May I recommend a pair of Aerial 5B speakers? They're an excellent value and make beautiful music. While they're not super efficient, they're not difficult to drive either. And they work very well is both small and large rooms.