To pricey

In this current climate is better to go with pro speakers and looks for speakers made from wood and not break the bank. Also to build your own speaker is quite easy today and the material is a little expensive but you can make it so much better for a few thousand on a custom speaker is nearly better than a 20000 speaker just saying also diminishing returns is a real thing 

definitely would not pick B&W, I find them a little bright and edgy.

the monitor audio platinum 200 and 300 Gen 2 and gen 3 are much better than anything B&W makes, much more natural sounding and way more three-dimensional.

I auditioned the new D4 (803/804) powered by Classe Audio and I didn’t like either of them but it could be the amplifications and the speakers were merely broken-in  (I used to own N802 and love it!)

IMHO you may want to consider upgrading the NAD amp which should give you much better sounding than going from N804 to 804D4 

James633 - I agree. The only way to make any B&W that I have heard listenable for any length of time is when you pair them up with a warmer sounding Classe or McIntosh amp. I’m pretty sure that why B&W bought Classe.