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 | Marantz Model 10 has more power - 250W against 150W into 8 ohms. That is about 2.2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Marantz Model 10 the better fit for a very large room, and Devialet Astra for desk or near-field listening, a small room and a mid-size room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output nearly doubles (500W and 300W). |
| Bass control | B | Devialet Astra has the higher damping factor (2000 vs 500), which usually means a tighter grip on a woofer. Above about 100 the returns flatten out, so read this as a tendency rather than a ranking. |
| Built-in DAC | B | Devialet Astra 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 10 takes more analogue sources - 6 against 2. |
| Room to grow | evenly matched | The same expansion options on both. |
| Headphones | depends | Only Marantz Model 10 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Marantz Model 10 is Class D and Devialet Astra is ADH (Analog Digital Hybrid). Class D runs cool and draws almost nothing at idle. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Devialet Astra takes up about 28% less shelf area (1490cm² against 2081cm²), and it is 87mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Marantz Model 10 costs less - $15,000 against $20,000 at list. |
| Watts per dollar | A | Marantz Model 10 is the cheaper watt - about $60 per watt against $133. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Marantz Model 10 B Devialet Astra
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 10 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. Start with the room. In a large or open-plan room, or with speakers that are hard to drive - low sensitivity, or an impedance that dips - Marantz Model 10 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 150 watts is already more than most people ever use, and the extra 100 watts would be headroom you pay for and never hear - we rate Marantz Model 10 poorly for near-field use for exactly that reason. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Marantz Model 10 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.