These are not the same size of amplifier: Michi X5 Series 2 has roughly 2.4x the power of Rega Osiris. That is about 3.9dB, 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 | Michi X5 Series 2 has more power - 390W against 160W into 8 ohms. That is about 3.9dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output increases strongly (250W and 600W). |
| Built-in DAC | B | Michi X5 Series 2 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | evenly matched | The same number of line-level inputs (5). |
| Phono stage | depends | Michi X5 Series 2 has a built-in phono stage (MM and MC) and Rega Osiris does not. Decisive if you own a turntable, completely irrelevant if you do not - and an outboard phono stage is easy to add later either way. |
| Shelf space | depends | Rega Osiris takes up about 31% less shelf area (1519cm² against 2192cm²), and it is 102mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Michi X5 Series 2 costs less - $9,499 against $11,600 at list. |
| Watts per dollar | B | Michi X5 Series 2 is the cheaper watt - about $24 per watt against $73. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Rega Osiris B Michi X5 Series 2
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?
Michi X5 Series 2 is the easier recommendation: it leads on most of the measured areas and costs less. Take Rega Osiris if one of the "depends" rows above describes your system. 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 - Michi X5 Series 2 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 160 watts is already more than most people ever use, and the extra 230 watts would be headroom you pay for and never hear - we rate Michi X5 Series 2 poorly for near-field use for exactly that reason. If you play records, Michi X5 Series 2 saves you buying a phono stage; if you do not, ignore that row entirely.
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.