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 - 80W against 70W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Grip on hard loads | A | Rotel S14 holds up better into a 4-ohm load: its output nearly doubles to 150W, 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 100dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board. Rotel S14 goes higher - 384kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | evenly matched | Only Rotel S14 has Chromecast; 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 1. |
| Phono stage | depends | Marantz Model 40n has a built-in phono stage (MM) and Rotel S14 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. |
| 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. |
| Room to grow | evenly matched | The same expansion options on both. |
| Shelf space | depends | Rotel S14 takes up about 23% less shelf area (1629cm² against 2126cm²), and it is 104mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | evenly matched | Priced within a few per cent of each other. |
A Rotel S14 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?
Neither runs away with it - they trade advantages. Let the "depends" rows and the speakers you already own settle it. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Rotel S14 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 interface feels 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.