[Yes, it will drive the B&W 803 very well. I own a pair of B&W 802D and had the NC400 mono blocks drive them with no sweat. It showed how much better the 802D could sound. When funds permit get a second pair of NC400 and drive the 803 in a bi-amp to the 803 and you will be in for a real sonic treat. Or get a pair of NC1200 mono blocks. They not only have two pairs of speaker output posts per mono amp but sound even better then the NC400. ]
Which ever way you go it will sound great.
[Thanks to all of you for your prompt answers and suggestions. I live in Macedonia. To be onest I am quite happy with the sound which I have in the moment, probably beside other thinks, due to the extensive DIY room treatment. However its part of our hobby end enjoyment to try from time to time and some other gear .Unfortunately second hand market in my country is quite limited and new gear is quite expensive according to the present living standard.