These are not the same size of amplifier: Sonos Amp has roughly 2.1x the power of Rotel A12. That is about 3.2dB, 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 | Sonos Amp has more power - 125W against 60W into 8 ohms. That is about 3.2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Sonos Amp the better fit for a mid-size room, a large room and a very large room, and Rotel A12 for desk or near-field listening and a small room. Match the amplifier to the room you actually have, not the one you want. |
| Noise floor | A | Sonos Amp is the quieter design on paper - 116dB against 100dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board. Rotel A12 goes higher - 192kHz against 44kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | evenly matched | Only Sonos Amp has AirPlay 2. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Analogue inputs | B | Rotel A12 takes more analogue sources - 4 against 1. |
| Phono stage | depends | Rotel A12 has a built-in phono stage (MM) and Sonos Amp 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. |
| Room to grow | evenly matched | The same expansion options on both. |
| Headphones | depends | Only Rotel A12 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Sonos Amp is Class D and Rotel A12 is Class A/B. Class D runs cool and draws almost nothing at idle; Class A/B runs warm and is the long-established mainstream choice. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Sonos Amp takes up about 68% less shelf area (518cm² against 1633cm²), and it is 140mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Sonos Amp costs less - $699 against $800 at list. |
| Watts per dollar | A | Sonos Amp is the cheaper watt - about $6 per watt against $13. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Sonos Amp B Rotel A12
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?
Sonos Amp 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 - Sonos Amp has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 60 watts is already more than most people ever use, and the extra 65 watts would be headroom you pay for and never hear - we rate Sonos Amp poorly for near-field use for exactly that reason. If you play records, Rotel A12 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 interface feels 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.