Power Cord for NAD C356DAC Int. Amplifier

Don't waste your money, as you'll never hear the difference.

IMO and personal experience with the NAD kit, it may incrementally help (s/t SYTSTEM SYNERGY ALCHEMY comments below) but only by a comparatively limited amount at the NAD's build quality / price point strata; so don't go overboard expecting a quantum leap improvement. Again $100 is your threshold max IMO.

The quality and performance output of this upgrade is variable and system-dependent. Any power cable upgrade to better performance exercise is only a very small part of an ethereal alchemy created by the synergy (or lack thereof) provided by all of:
(i) your source,
(ii) the electronics themselves,
(iii) all the cables (Power/ ICs and speaker);
(iv) your speakers, and
(v)the listening room environment warts itself.

One "change" factor by itself alone may -- or may not --have a desired positive effect. Alternatively it may have no effect, or even be an adverse effect. This is a journey and not a destination exercise with a trial and error factor as its mantra.

I'm sure the stock power cord is more than adequate. But if you feel you must buy something, get one of the Pangea 14 ga. cords. They are quite reasonably priced around $50...

Any aftermarket PC I've tried sounded better than the stock one that came with the amp (better dynamics and increased soundstage were readily apparent).
You don't have to go overboard and need look no further than here on A'gon.
Try either of these and you'll be happy:
http://app.audiogon.com/listings/ac-cables-cullen-cable-1-5-meter-12-awg-power-cable-silver-plated-made-in-the-usa-2015-01-08-power-93422-atascadero-ca--2
or
http://app.audiogon.com/listings/ac-cables-signalcable-magicpower-cord-2015-01-06-power-11577-roslyn-heights-ny

All the best,
Npnoise

Go with a Pangea 14 from Audio Advisor. Better than stock and inexpensive.