These are not the same size of amplifier: Sonos Amp has roughly 2.3x the power of Yamaha WXA-50. That is about 3.6dB, 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 | Sonos Amp has more power - 125W against 55W into 8 ohms. That is about 3.6dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Yamaha WXA-50 the better fit for desk or near-field listening and a small room, and Sonos Amp for a mid-size room, a large room and a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output nearly doubles (105W and 250W). |
| Noise floor | B | Sonos Amp is the quieter design on paper - 116dB against 110dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board. Yamaha WXA-50 goes higher - 192kHz against 44kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | B | Only Yamaha WXA-50 has MusicCast; only Sonos Amp has AirPlay 2, Sonos, Qobuz, Apple Music and iHeartRadio. |
| Analogue inputs | evenly matched | The same number of line-level inputs (1). |
| Use with a TV | depends | Only Sonos Amp has HDMI ARC, so the television can drive it directly and one remote controls the volume. If the system is for music only, this changes nothing. |
| Room to grow | evenly matched | The same expansion options on both. |
| Price | A | Yamaha WXA-50 costs less - $599 against $699 at list. |
| Watts per dollar | B | Sonos Amp is the cheaper watt - about $6 per watt against $11. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Yamaha WXA-50 B Sonos Amp
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 leads across most of the measured areas for a fairly modest premium, so it is the easier pick if the budget stretches. Yamaha WXA-50 is the one to take if it does not. 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, 55 watts is already more than most people ever use, and the extra 70 watts would be headroom you pay for and never hear - we rate Sonos Amp poorly for near-field use for exactly that reason. If this sits under a television, Sonos Amp is the one to buy - HDMI ARC means the TV remote controls the volume and there is no second box in the way.
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.