Different price classes - Devialet Astra costs roughly 1.8x what MOON 641 does. Expect it to lead on paper; the question is whether you will hear the difference through the speakers you own.
| Area | Better | Why |
|---|
| Power | evenly matched | Effectively the same output - 150W against 125W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output nearly doubles (300W and 250W). |
| Bass control | A | Devialet Astra has the higher damping factor (2000 vs 700), 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 | A | 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 | B | MOON 641 takes more analogue sources - 5 against 2. |
| Amplifier class | depends | Devialet Astra is ADH (Analog Digital Hybrid) and MOON 641 is Class A/B. 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 | Devialet Astra takes up about 33% less shelf area (1490cm² against 2239cm²), and it is 79mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | MOON 641 costs less - $11,000 against $20,000 at list. |
| Watts per dollar | B | MOON 641 is the cheaper watt - about $88 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 Devialet Astra B MOON 641
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 you already own a DAC or a streamer, the built-in one is money you are paying twice for, and MOON 641 becomes the more rational buy. Think about the whole system: the roughly $9,000 saved by taking the cheaper one would buy better speakers or a subwoofer, which does more for the sound than the difference between two competent amplifiers.
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.