No single best amplifier here. What decides it is what you have to drive, what you need to plug in, and how much of the system you want in one box.
| Area | Better | Why |
|---|
| Zones | evenly matched | Both cover 4 stereo zones, from 8 channels. On this axis they are the same product, so the rest of the table decides it. |
| How the power is measured | evenly matched | Both publish an all-channels-driven rating, so the watts row above is a fair comparison rather than two different tests side by side. |
| Power | A | Sonos Amp Multi 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. |
| Bass control | A | Sonos Amp Multi has the higher damping factor (400 vs 80), which usually means a tighter grip on a woofer. Above about 100 the returns flatten out, so read this as a tendency rather than a ranking. |
| Noise floor | A | Sonos Amp Multi is the quieter design on paper - 114dB against 100dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board. Rotel C8+ goes higher - 192kHz against 44kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Analogue inputs | B | Rotel C8+ takes more analogue sources - 4 against 2. |
| Amplifier class | depends | Sonos Amp Multi is Class D and Rotel C8+ 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 Multi takes up about 35% less shelf area (1158cm² against 1780cm²), and it is 149mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | evenly matched | Priced within a few per cent of each other. |
A Sonos Amp Multi B Rotel C8+
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 Multi has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is.
What a spec sheet cannot show: how either sounds with your speakers, how the controls feel day to day, and how the zone control and setup behave once it is in a rack - which is where a distribution amplifier is actually lived with. 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.