These are not the same size of amplifier: MOON 641 has roughly 2.5x the power of MOON 250i v2. That is about 4dB, so it is a question of room size and how hard your speakers are to drive, not of one being the better amplifier.
| Area | Better | Why |
|---|
| Power | B | MOON 641 has more power - 125W against 50W into 8 ohms. That is about 4dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate MOON 250i v2 the better fit for desk or near-field listening and a small room, and MOON 641 for a mid-size room, a large room and a very large 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 (100W and 250W). |
| Noise floor | B | MOON 641 is the quieter design on paper - 109dB against 101dB. Audible mainly with sensitive speakers in a quiet room. |
| Analogue inputs | A | MOON 250i v2 takes more analogue sources - 6 against 5. |
| Headphones | depends | Only MOON 250i v2 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Shelf space | depends | MOON 250i v2 takes up about 30% less shelf area (1570cm² against 2239cm²), and it is 100mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | MOON 250i v2 costs less - $2,400 against $11,000 at list. |
| Watts per dollar | A | MOON 250i v2 is the cheaper watt - about $48 per watt against $88. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A MOON 250i v2 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. 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 - MOON 641 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 50 watts is already more than most people ever use, and the extra 75 watts would be headroom you pay for and never hear - we rate MOON 641 poorly for near-field use for exactly that reason. Think about the whole system: the roughly $8,600 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.