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 - 70W against 70W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Grip on hard loads | B | Denon PMA-1700NE holds up better into a 4-ohm load: its output nearly doubles to 140W, where the other increases modestly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | A | Marantz Model 50 is the quieter design on paper - 113dB against 107dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Denon PMA-1700NE has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | A | Marantz Model 50 takes more analogue sources - 5 against 3. |
| Room to grow | A | Only Marantz Model 50 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Price | A | Marantz Model 50 costs less - $1,800 against $2,099 at list. |
A Marantz Model 50 B Denon PMA-1700NE
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 50 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 - Denon PMA-1700NE is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Marantz Model 50 becomes the more rational buy.
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.