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 | A | NAD Masters Series M10 V2 has more power - 100W against 70W into 8 ohms. That is about 1.5dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate NAD Masters Series M10 V2 the better fit for a large room and a very large room, and Marantz Model 40n for a small room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | B | Marantz Model 40n holds up better into a 4-ohm load: its output increases modestly to 100W, where the other barely increases. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | B | Marantz Model 40n is the quieter design on paper - 106dB against 90dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board, but only NAD Masters Series M10 V2 handles MQA. |
| Streaming | evenly matched | Only NAD Masters Series M10 V2 has BluOS; only Marantz Model 40n has HEOS. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Analogue inputs | B | Marantz Model 40n takes more analogue sources - 3 against 2. |
| Phono stage | depends | Marantz Model 40n has a built-in phono stage (MM) and NAD Masters Series M10 V2 does not. Decisive if you own a turntable, completely irrelevant if you do not - and an outboard phono stage is easy to add later either way. |
| Room to grow | evenly matched | The same expansion options on both. |
| Headphones | depends | Only Marantz Model 40n has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | NAD Masters Series M10 V2 is Class D and Marantz Model 40n 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 Masters Series M10 V2 takes up about 71% less shelf area (606cm² against 2126cm²), and it is 203mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Marantz Model 40n costs less - $2,499 against $2,999 at list. |
A NAD Masters Series M10 V2 B Marantz Model 40n
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 Model 40n has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Marantz Model 40n is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If you play records, Marantz Model 40n saves you buying a phono stage; if you do not, ignore that row entirely.
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.