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 | Musical Fidelity M2si has more power - 76W against 50W into 8 ohms. That is about 1.8dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate Musical Fidelity M2si the better fit for a mid-size room, a large room and a very large room, and Audiolab 6000A MKII for desk or near-field listening and a small room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | A | Musical Fidelity M2si holds up better into a 4-ohm load: its output nearly doubles to 137W, where the other increases strongly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | B | Audiolab 6000A MKII is the quieter design on paper - 110dB against 96dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Audiolab 6000A MKII has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | A | Musical Fidelity M2si takes more analogue sources - 5 against 3. |
| Headphones | depends | Only Audiolab 6000A MKII has a headphone output. Worth something if you listen late, nothing if you never do. |
| Shelf space | depends | Audiolab 6000A MKII takes up about 25% less shelf area (1328cm² against 1760cm²), and it is 101mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Audiolab 6000A MKII costs less - $1,099 against $1,299 at list. |
| Watts per dollar | A | Musical Fidelity M2si is the cheaper watt - about $17 per watt against $22. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Musical Fidelity M2si B Audiolab 6000A MKII
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: Musical Fidelity M2si measures better, Audiolab 6000A MKII costs about 15% 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 - Musical Fidelity M2si 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 Musical Fidelity M2si 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.