I can tell you I just bought a new M3 and investigated it heavily, including several calls to NAD. I think the key is to where it is designed, and what level of QC the designing manufacturer is holding the plant to. Many North American major audio and smaller audio companies are building in China. Probably some that we do not readily know of. I during my search, discussed with another audio company, thier expensive integrated amp, and it being made in China. His feeling was that designed in North America, built in China with the right quality control, is as good as being built anywhere else.
My Mac preamp had a volume control failure within 5 years, so everything can fail.
But back to NAD and the M3. That is an NAD design in Canada with proprietary NAD items, not a China design rebadged like some of the audio products showing up. Of all the Dealers I talked to, there have been few problems overall on the M3 from what I gathered. There were some early problems with the M55/M5 I guess, but that was resolved. If I am not mistaken Mac had issues with it's 201 SACD player, and Rega had issues with some of it's CD players , so again nobody is immune.
I did a lot of research into products, failures, performance etc. What I found was of the 4 or 5 integrated amps I researched on, not one of them had a clean record. By that I mean, complaints of failure or flawed sonics of one type or another shows up on all of them, including the NAD M3. There is always some complaint or issue on all. So I found you have to take it all with a grain of salt and make your best decision.
All this said and done, I'll post on how well I like my M3 in the following days, and how it works and sounds.