Rob,
I have been using a NAD 3140 integrated amp for the past 23 years, pretty much daily or every other day. The only trouble (besides dirty contacts in unused switches) was a hum in the left channel that lasted a few minutes after turn on, which developed a few years ago. It went away some months lager, after I seriously threatened it with looking for a replacement. It sounds great, mostly running under 1 watt on my 27 year old big monitors unless I crank a big symphony. Similar to Sushi's "beloved Hales" I have my "beloved Qysonics." Of course this does not speak to the recent NAD gear but the 320BEE is supposed to take after their old designs.
I have a pair of M3Ti that also sound good on the NAD, but mostly they live in another room and are run by a 50 watt/ch JBL power amp. They are efficient enough that 40 or 50 watts is plenty of oomph. But you may run out of gas on the 320BEE if you want to go really loud. If you can get it from somewhere that will let you return it if not satisfied, or take it for a demo, that would be best.
