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 | Arcam A15 has more power - 80W against 50W into 8 ohms. That is about 2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Arcam A15 the better fit for a mid-size room, a large room and a very large room, and Rega Brio for desk or near-field listening and a small room. Match the amplifier to the room you actually have, not the one you want. |
| Built-in DAC | A | Arcam A15 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | B | Rega Brio takes more analogue sources - 4 against 3. |
| Room to grow | A | Only Arcam A15 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Shelf space | depends | Rega Brio takes up about 53% less shelf area (745cm² against 1580cm²). |
| Price | A | Arcam A15 costs less - $999 against $1,100 at list. |
| Watts per dollar | A | Arcam A15 is the cheaper watt - about $12 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 Arcam A15 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?
Arcam A15 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. 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 - Arcam A15 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 30 watts would be headroom you pay for and never hear - we rate Arcam A15 poorly for near-field use for exactly that reason. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Rega Brio 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.