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 75W into 8 ohms. That is about 2.2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate SVS Prime SoundBase the better fit for a small room, and Sonos Amp for 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 (150W and 250W). |
| Noise floor | B | Sonos Amp is the quieter design on paper - 116dB against 90dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board. SVS Prime SoundBase goes higher - 192kHz against 44kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | A | Only SVS Prime SoundBase has Chromecast and DTS Play-Fi. |
| Analogue inputs | A | SVS Prime SoundBase takes more analogue sources - 2 against 1. |
| Room to grow | evenly matched | The same expansion options on both. |
| Headphones | depends | Only SVS Prime SoundBase has a headphone output. Worth something if you listen late, nothing if you never do. |
| Price | evenly matched | Priced within a few per cent of each other. |
| Watts per dollar | B | 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 SVS Prime SoundBase 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. 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, 75 watts is already more than most people ever use, and the extra 50 watts would be headroom you pay for and never hear - we rate Sonos Amp poorly for near-field use for exactly that reason.
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.