These are not the same size of amplifier: Rega Osiris has roughly 3.2x the power of Rega Brio. That is about 5.1dB, 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 | A | Rega Osiris has more power - 160W against 50W into 8 ohms. That is about 5.1dB - a different class of amplifier rather than a bigger version of the same one, and far more than most rooms will ever ask for. |
| Room size | depends | We rate Rega Osiris the better fit for a large room and a very large room, and Rega Brio for desk or near-field listening, a small room and a mid-size room. Match the amplifier to the room you actually have, not the one you want. |
| Analogue inputs | A | Rega Osiris takes more analogue sources - 5 against 4. |
| Phono stage | depends | Rega Brio has a built-in phono stage (MM) 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. |
| Headphones | depends | Only Rega Brio has a headphone output. Worth something if you listen late, nothing if you never do. |
| Shelf space | depends | Rega Brio takes up about 51% less shelf area (745cm² against 1519cm²). |
| Price | B | Rega Brio costs less - $1,100 against $11,600 at list. |
| Watts per dollar | B | Rega Brio is the cheaper watt - about $22 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 Rega Brio
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?
Rega Osiris is ahead, but on only 1 of the measured areas, and it costs about 10.5x the price. That is a lot of money for a narrow margin - Rega Brio is the sensible buy unless a specific feature above decides it for you. 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 - Rega Osiris 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 110 watts would be headroom you pay for and never hear - we rate Rega Osiris poorly for near-field use for exactly that reason. If you play records, Rega Brio 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.