Hello dbphd,
Happy Independence Day!
I'm very glad you like the performance of the class D NAD M22 driving your KEF LS50s.
I appreciate good class D amps for their very low noise floor, good bass and dynamics along with the very accurate, detailed and neutral midrange/treble response that still manages to be smooth and natural without ever being bright or harsh. I've found them to be very close to the audio ideal of 'a straight wire with gain'; with nothing added, subtracted or altered from the inputted signals.
This accuracy and neutrality sounds great on good recordings and matched with high quality upstream components but it also will clearly amplify any faults in the sound caused by poor recordings and poor quality upstream components. Personally, I prefer this accuracy and neutrality but I thought you should be aware of this quality of good class D amps if you weren't already. Fortunately, you have high quality components so you'll only need to be concerned with the quality of your music recordings and other audio sources.
Well, so far so good, right? I'm looking forward to hearing your impressions once everything's completed, especially the four subs and how the bass sounds and integrates.
Later,
Tim