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.