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 - 76W against 80W 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 (137W and 150W). |
| Noise floor | B | Rotel A14 MKII is the quieter design on paper - 100dB against 96dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Rotel A14 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 4. |
| Headphones | depends | Only Rotel A14 MKII has a headphone output. Worth something if you listen late, nothing if you never do. |
| Price | A | Musical Fidelity M2si costs less - $1,299 against $1,600 at list. |
A Musical Fidelity M2si B Rotel A14 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: Rotel A14 MKII measures better, Musical Fidelity M2si costs about 19% less. With most speakers in most rooms that gap is smaller in practice than it looks here. 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.