One is a streaming all-in-one and the other is an amplifier. Judge them on how many boxes you want and what you already own, not on the spec sheet alone.
| Area | Better | Why |
|---|
| Power | B | Sonos Amp has more power - 125W against 100W into 8 ohms. That is about 1dB, which is a small step in loudness but real headroom on peaks. |
| Built-in DAC | A | Both decode on board, but only Denon DRA-900H handles DSD. |
| Streaming | evenly matched | Only Denon DRA-900H has HEOS. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Analogue inputs | A | Denon DRA-900H takes more analogue sources - 2 against 1. |
| Phono stage | depends | Denon DRA-900H 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. |
| Amplifier class | depends | Denon DRA-900H is Class A/B and Sonos Amp is Class D. Class A/B runs warm and is the long-established mainstream choice; Class D runs cool and draws almost nothing at idle. 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 1615cm²), and it is 132mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Sonos Amp costs less - $699 against $799 at list. |
| Watts per dollar | B | Sonos Amp is the cheaper watt - about $6 per watt against $8. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Denon DRA-900H 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?
Neither runs away with it - they trade advantages. Let the "depends" rows and the speakers you already own settle it. If you play records, Denon DRA-900H 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.