Stay away from the nad

   Contacting NAD about your unit is a good idea. There's always going to be some premature failure rate in almost any product. You just got a bad one, that's all. I wouldn't condemn the entire company over one bad unit. 

With 3 amps dying on you, something must be wrong in your system, or house wiring.

What ohm rating do your speakers have? Do they have a phase angle? Did you buy brand new Nad each time or factory refurbs? What specific volume level position do you use? And for how many hours at a time?

It just seems strange to me. I’ve owned 5 Nad integrated amps. 2 C326BEE, one c372, one C375BEE and one C356BEE. And a top of the line cd player, the C565BEE. Three were used. Two were refurbs, and one was brand new. I’ve only owned each for a year or so, but I’ve not had one failure. Now, could I be extremely lucky, and Nad is actually awful, or much more likely, Nad has been around for over 40 years for a good reason, and something else is going on.  Still, your experience sucks, and I can understand wanting to stay away from Nad.

PS, the $400 estimate over the phone from the service center, is useless since they don’t really know what the problem with the C356BEE is. It could be more, but most likely a lot less.

These are not rare cases, this has plagued NAD for the past few years, something to do with quality control. If you buy anything from them its hit or miss. This is very unfortunate situation since they make very good sounding units.

+1 m-db!

Same here with a 315bee integrated.  Good sound for the money, but built with components so cheap and assembled so badly that it did not last much longer than a year.  The entire pre-amp was totally shorted, inputs, volume control, etc... in a more than caring environment. 
So for me, never NAD again.  In addition, the new classic line hybrid digital have not been well received by reviewers.
imho, NAD is not going stay one the market much longer.  They have made the wrong choices when it come to quality control and designs.