Clipping with Separates with change of Power Conditioner[?]

I’d just plug the amp right into the wall, as recommended above. 80 Watts of rated power isn’t much. BUT - Class D amplifiers can have very high instantaneous peak power & current demands, and your new conditioner may be limiting this - perhaps the NAD’s protection circuitry (more likely the Hypex module circuitry) doesn’t like these conditions, hence the shutdown.

When running an amp, you want a power condition that is NOT "current limiting". But frankly, I often find it best to simply run amps directly off the wall (if available). I’ve never had a problem doing this, and feel that most of the supposed benefits of expensive power conditioning are way oversold (and I have a Niagara 7000).

Ironically, if your amp were class A it would have a continuous constant power draw, no matter the signal level.

I’m a big believer in isolation transformers.  Really clean up the sound. I use a large 20amp Equi=Tech balanced isolation transformer unit for my preamp, etc.  I would still plug my mono-block  tube amps directly into the wall until I found a couple of 8 amp isolation transformers to plug each in to which has worked very nicely.  Just sound cleaner.  I also have a couple of smaller (5amp) isolation transformers that I plug all the little wall warts, etc into the power the network switch, light, turntable, etc.  This keeps digital crap from getting back into the line. 
Makes for a very quiet system. 

Even better consider a dedicated line from the breaker box to your listening room. Got rid of all hum from dimmers, large appliances, etc. Dropped the noise floor too. Improved clarity, inner details and soundstage.

Tomcarr - Yes you are correct. I have (3) 20amp lines wired directly from the breaker box. Oversized copper conduit with Furutech AC Rhodium plated outlets. Then of course good AC cabling to the isolation transformers. I’ve also replaced the outlet in the transformers with Furutech AC sockets and rewired them internally.

Naturally there's always better and more you can do.  This is the best I can afford for now.  But always adding little tweaks as I come across deals on things I can add. 

just to be clear, I recommended plugging into the wall to troubleshoot.  I do believe in a quality power regenerator.  but my regenerator costs 6X what your amp costs so in your price range, plugging into the wall is probably your best option.  don't use a surge protector if you can avoid it.  Better option is to unplug when lightning is in the area.  Surge protectors don't always protect you or maybe usually don't protect you.  but they give a lot of people peace of mind (perhaps undeservedly).  

Also, as for a dedicated line, you may already have one.  You have 3 outlets in the room you think are on the same circuit.  open the breaker and see what else de-energizes.  if there is nothing else on the circuit, then your noise level should be minimal.  If there are outlets in another room, try not to use them.  If there are lights, make sure they don't have a dimmer switch and keep them off when listening. If there are important items you can't do without that are making noise or pulling a lot of power, then you may need a dedicated line.

Jerry