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 | A | 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. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output nearly doubles (250W and 200W). |
| Noise floor | A | Sonos Amp is the quieter design on paper - 116dB against 96dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board. AudioControl Rialto 600 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 | evenly matched | The same number of line-level inputs (1). |
| Room to grow | evenly matched | The same expansion options on both. |
| Headphones | depends | Only AudioControl Rialto 600 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Shelf space | depends | AudioControl Rialto 600 takes up about 21% less shelf area (410cm² against 518cm²), and it is 50mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Sonos Amp costs less - $699 against $899 at list. |
| Watts per dollar | A | Sonos Amp is the cheaper watt - about $6 per watt against $9. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Sonos Amp B AudioControl Rialto 600
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 is the easier recommendation: it leads on most of the measured areas and costs less. Take AudioControl Rialto 600 if one of the "depends" rows above describes your system.
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.