These are not the same size of amplifier: Cambridge Audio Evo 300 has roughly 2x the power of Cambridge Audio Evo 150. That is about 3dB, so it is a question of room size and how hard your speakers are to drive, not of one being the better amplifier.
| Area | Better | Why |
|---|
| Power | B | Cambridge Audio Evo 300 has more power - 300W against 150W into 8 ohms. That is about 3dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Grip on hard loads | B | Cambridge Audio Evo 300 holds up better into a 4-ohm load: its output nearly doubles to 550W, where the other increases strongly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Built-in DAC | B | 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 | evenly matched | The same streaming platforms and services on both. |
| Room to grow | evenly matched | The same expansion options on both. |
| Shelf space | depends | Cambridge Audio Evo 150 takes up about 19% less shelf area (1190cm² against 1463cm²). |
| Price | A | Cambridge Audio Evo 150 costs less - $3,249 against $3,999 at list. |
| Watts per dollar | B | Cambridge Audio Evo 300 is the cheaper watt - about $13 per watt against $22. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Cambridge Audio Evo 150 B Cambridge Audio Evo 300
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 leads across most of the measured areas for a fairly modest premium, so it is the easier pick if the budget stretches. Cambridge Audio Evo 150 is the one to take if it does not. 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. 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 - Cambridge Audio Evo 300 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 150 watts is already more than most people ever use, and the extra 150 watts would be headroom you pay for and never hear.
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.