No single best amplifier here. What decides it is what you have to drive, what you need to plug in, and how much of the system you want in one box.
| Area | Better | Why |
|---|
| Power | evenly matched | Effectively the same output - 40W against 45W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Room size | depends | We rate NAD C 328 the better fit for desk or near-field listening, and Denon PMA-600NE for a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Noise floor | B | Denon PMA-600NE is the quieter design on paper - 105dB against 100dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Analogue inputs | B | Denon PMA-600NE takes more analogue sources - 4 against 2. |
| Room to grow | evenly matched | The same expansion options on both. |
| Amplifier class | depends | NAD C 328 is Class D and Denon PMA-600NE is Class A/B. Class D runs cool and draws almost nothing at idle; Class A/B runs warm and is the long-established mainstream choice. Modern examples of both measure well - judge by the rest of the page. |
| Price | B | Denon PMA-600NE costs less - $499 against $699 at list. |
| Watts per dollar | B | Denon PMA-600NE is the cheaper watt - about $11 per watt against $17. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A NAD C 328 B Denon PMA-600NE
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both amplifiers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Denon PMA-600NE is the easier recommendation: it leads on most of the measured areas and costs less. Take NAD C 328 if one of the "depends" rows above describes your system. Think about the whole system: the roughly $200 saved by taking the cheaper one would buy better speakers or a subwoofer, which does more for the sound than the difference between two competent amplifiers.
What a spec sheet cannot show: how either sounds with your speakers, how the controls feel day to day, and what the app is like to live with - which is where most all-in-one amplifiers are actually won or lost. Power figures are the manufacturers' own and are not measured to a common standard, so treat small differences as noise. If you can hear both, that will tell you more than any row above.