Actually is 105dB, a single speaker. 105+6=> 111dB.
You can see Stereoplay measurements for check the number, it's the same number that provided by kef.
As a user i never noticed distortion since i'm in a little room, i don't need that much volume, that being said i have a pretty heavy in-room EQ and when i cranck them up the volume i never noticed the any distortion in the bass, i guess i'm a bit far for the max volume.
My R300s were another history, these started to do weird bass noises at 120hz~ at much lower volume, a very different quality of woofers between 2012~ series and the 2018~ series.