@daveteauk thanks for your input.
First about the Naim: I completely disagree. All components can be “bad sounding” if the synergy isn’t there in the first place, The Nac122x is a wonderful piece and must be used with the Flatcap 2x for the best results. One example of a mismatch: my Belles Soloist 1 integrated is wonderful with the Totem Model 1 speakers (another demanding speaker) and is completely wrong with the LRS+. Is is a cheap garbage piece? Absolutely not.
The Naim combo give me amazing results with the Totem, Kef LS50, Duevel Planets, Quad 11L and it is the most successful amp (in my lot) with the LRS+.
The 1,5 Ohm Mundorf resistor improved the treble significantly. Now I am readjusting the positioning…
Oh, and my dedicated listening room is professionally treated by Vicoustic.