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 | Marantz Model 30 has more power - 100W against 75W into 8 ohms. That is about 1.2dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate Marantz Model 30 the better fit for a large room and a very large room, and Cambridge Audio Evo 75 for a small 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 (200W and 150W). |
| Built-in DAC | B | Cambridge Audio Evo 75 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Streaming | B | Only Cambridge Audio Evo 75 has AirPlay 2, Chromecast and Roon. |
| Analogue inputs | A | Marantz Model 30 takes more analogue sources - 6 against 1. |
| Phono stage | depends | Marantz Model 30 has a built-in phono stage (MM,MC) and Cambridge Audio Evo 75 does not. Decisive if you own a turntable, completely irrelevant if you do not - and an outboard phono stage is easy to add later either way. |
| Room to grow | evenly matched | The same expansion options on both. |
| Shelf space | depends | Cambridge Audio Evo 75 takes up about 41% less shelf area (1190cm² against 2033cm²), and it is 87mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Cambridge Audio Evo 75 costs less - $2,499 against $2,999 at list. |
A Marantz Model 30 B Cambridge Audio Evo 75
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. If you play records, Marantz Model 30 saves you buying a phono stage; if you do not, ignore that row entirely. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Marantz Model 30 becomes the more rational buy.
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.