You should be fine with Classe 400M mono amps. You should also consider getting a matching preamp. That Marantz receiver is way out of its league there.
Amp for B&W 802N
I am looking at purchasing a pair of class audio amps. The CA-M400 mono blocks are what I am looking at. Used of course. Looking for opinions on this. I am currently using a Marantz 6011 receiver and a Emotiva amp and B&W 802N speakers. It sounds good. But of course I am looking for the next level. (Please, no negative comments about the emotiva amp. It has worked well) Looking forwarding to some great advice.