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 | Cambridge Audio Evo 300 has more power - 300W against 235W into 8 ohms. That is about 1.1dB, which is a small step in loudness but real headroom on peaks. |
| Grip on hard loads | A | Cambridge Audio Evo 300 holds up better into a 4-ohm load: its output nearly doubles to 550W, where the other increases modestly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Built-in DAC | A | Both decode on board. Cambridge Audio Evo 300 goes higher - 768kHz against 384kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | A | Only Cambridge Audio Evo 300 has AirPlay 2 and Chromecast. |
| Use with a TV | depends | Only Cambridge Audio Evo 300 has HDMI, 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. |
| Amplifier class | depends | Cambridge Audio Evo 300 is Class D and Rotel Diamond RA-6000 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 | Cambridge Audio Evo 300 takes up about 26% less shelf area (1463cm² against 1979cm²), and it is 80mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Cambridge Audio Evo 300 costs less - $3,999 against $4,499 at list. |
| Watts per dollar | A | Cambridge Audio Evo 300 is the cheaper watt - about $13 per watt against $19. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Cambridge Audio Evo 300 B Rotel Diamond RA-6000
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?
Cambridge Audio Evo 300 is the easier recommendation: it leads on most of the measured areas and costs less. Take Rotel Diamond RA-6000 if one of the "depends" rows above describes your system. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Cambridge Audio Evo 300 is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If this sits under a television, Cambridge Audio Evo 300 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 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.