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 - 50W against 60W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Grip on hard loads | B | Marantz PM7000N holds up better into a 4-ohm load: its output increases modestly to 80W, where the other barely increases. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | B | Marantz PM7000N is the quieter design on paper - 115dB against 90dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board. NAD C3030S goes higher - 384kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | evenly matched | Only NAD C3030S has BluOS; only Marantz PM7000N has HEOS. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Room to grow | B | Only Marantz PM7000N offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Amplifier class | depends | NAD C3030S is Class D and Marantz PM7000N 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. |
| Shelf space | depends | NAD C3030S takes up about 28% less shelf area (1208cm² against 1684cm²), and it is 43mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Marantz PM7000N costs less - $1,299 against $1,499 at list. |
| Watts per dollar | B | Marantz PM7000N is the cheaper watt - about $22 per watt against $30. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A NAD C3030S B Marantz PM7000N
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?
Marantz PM7000N is the easier recommendation: it leads on most of the measured areas and costs less. Take NAD C3030S if one of the "depends" rows above describes your system. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Marantz PM7000N is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating.
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.