Power Amp suggestion

Your speaker is what you hear, Bryston matches well with PMC (IB2se, MB2se), and that direction i would follow.

G

I tried  bryston amp with arc ref3 and did not like combination of it.Arc sounds neutral,bryston neutral.Either amp or preamp needs to be changed.If for amps I would look to something warmer souding or warmer fuller sounding preamp

Someone on here recently (maybe @erik_squires?) said try and listen to 3 amps...Ayre, Luxman and Pass.  They are different presentations. I wouldn't say to choose one of those but you will probably like one more than the other two. That gives you an indication of what sound you like and people can give you better and more accurate advice. 

I would consider speakers before amps too, that may change your direction on amp selection too.  Unfortunately the B&Ws are very hungry, you need a lot of power for those.  A big Pass or McIntosh would be nice.  I think the big name Swiss brands are very overrated (I’ve heard many).  However, I would consider new speakers that are more efficient and then replace the Bryson with maybe an ARC Ref160.  
How do you like the DAVE DAC?  I’m considering one.  Are running the Nucleus into the DAVE directly through USB?  

@sbank 

while Bryston may build something to last 20 years, McIntosh builds to last a couple of lifetimes.