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 C 3050 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. |
| Grip on hard loads | B | Marantz Model 50 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 50 is the quieter design on paper - 113dB against 95dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | NAD C 3050 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Use with a TV | depends | Only NAD C 3050 has HDMI, 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 | A | Only NAD C 3050 offers a pre-out/main-in loop - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Amplifier class | depends | NAD C 3050 is Class D and Marantz Model 50 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 C 3050 takes up about 18% less shelf area (1633cm² against 2002cm²), and it is 90mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Marantz Model 50 costs less - $1,800 against $1,899 at list. |
| Watts per dollar | A | NAD C 3050 is the cheaper watt - about $19 per watt against $26. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A NAD C 3050 B Marantz Model 50
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?
The usual trade-off: NAD C 3050 measures better, Marantz Model 50 costs about 5% less. With most speakers in most rooms that gap is smaller in practice than it looks here. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Marantz Model 50 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, NAD C 3050 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.