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 |
|---|
| Power | A | Parasound JCM250 has more power - 250W against 150W into 8 ohms. That is about 2.2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output increases strongly (450W and 250W). |
| Built-in DAC | B | Cambridge Audio Evo 150 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | evenly matched | The same number of line-level inputs (2). |
| Phono stage | depends | Cambridge Audio Evo 150 has a built-in phono stage (MM) and Parasound JCM250 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. |
| Use with a TV | depends | Only Cambridge Audio Evo 150 has HDMI ARC, so the television can drive it directly and one remote controls the volume. If the system is for music only, this changes nothing. |
| Headphones | depends | Only Cambridge Audio Evo 150 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Parasound JCM250 is Class A/AB and Cambridge Audio Evo 150 is Class D. Class D runs cool and draws almost nothing at idle. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Cambridge Audio Evo 150 takes up about 47% less shelf area (1190cm² against 2226cm²), and it is 136mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Cambridge Audio Evo 150 costs less - $3,249 against $4,250 at list. |
| Watts per dollar | A | Parasound JCM250 is the cheaper watt - about $17 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 Parasound JCM250 B Cambridge Audio Evo 150
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?
The usual trade-off: Parasound JCM250 measures better, Cambridge Audio Evo 150 costs about 24% less. With most speakers in most rooms that gap is smaller in practice than it looks here. 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 - Parasound JCM250 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 100 watts would be headroom you pay for and never hear - we rate Parasound JCM250 poorly for near-field use for exactly that reason. If you play records, Cambridge Audio Evo 150 saves you buying a phono stage; if you do not, ignore that row entirely.
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.