I bought a pair of the 520's for my daughter and tried them in my system for awhile before shipping on to her. Compared to any of the other speakers I own the Ushers are a little bright so for my ears they need some warmth upstream.
I don't have any experience with the specific NAD or Cambridge amps you're considering but I'm a fan of the Decco. I use one as a preamp/DAC with an external tube power amp in the winter and as a stand-alone integrated in the summer. The versatility and sonic quality are great. The build quality is about the same as the Cambridge integrated I used to own, or the NAD stuff.
A lot of people love NAD gear but I had reliability issues with three out of the four pieces of NAD gear I've owned.
I don't have any experience with the specific NAD or Cambridge amps you're considering but I'm a fan of the Decco. I use one as a preamp/DAC with an external tube power amp in the winter and as a stand-alone integrated in the summer. The versatility and sonic quality are great. The build quality is about the same as the Cambridge integrated I used to own, or the NAD stuff.
A lot of people love NAD gear but I had reliability issues with three out of the four pieces of NAD gear I've owned.