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 | B | Marantz Model 40n has more power - 70W against 50W 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 MOON 250i v2 the better fit for desk or near-field listening and a small room, and Marantz Model 40n for a mid-size room, a large room and a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | A | MOON 250i v2 holds up better into a 4-ohm load: its output nearly doubles to 100W, where the other increases modestly. 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 101dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Marantz Model 40n has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | A | MOON 250i v2 takes more analogue sources - 6 against 3. |
| Use with a TV | depends | Only Marantz Model 40n has HDMI ARC, so the television can drive it directly and one remote controls the volume. If the system is for music only, this changes nothing. |
| Shelf space | depends | MOON 250i v2 takes up about 26% less shelf area (1570cm² against 2126cm²), and it is 115mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | evenly matched | Priced within a few per cent of each other. |
| Watts per dollar | B | Marantz Model 40n is the cheaper watt - about $36 per watt against $48. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A MOON 250i 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 - MOON 250i v2 is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If this sits under a television, Marantz Model 40n is the one to buy - HDMI ARC means the TV remote controls the volume and there is no second box in the way.
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.