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 | B | Arcam A25 has more power - 100W against 80W into 8 ohms. That is about 1dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate Cambridge CXA81 II the better fit for a small room, and Arcam A25 for a large room and a very large 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 increases strongly (120W and 165W). |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (105dB vs 106dB). |
| Built-in DAC | A | Both decode on board, but only Cambridge CXA81 II handles DSD. |
| Streaming | evenly matched | Only Cambridge CXA81 II has Roon. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Analogue inputs | A | Cambridge CXA81 II takes more analogue sources - 5 against 3. |
| Phono stage | depends | Arcam A25 has a built-in phono stage (MM) and Cambridge CXA81 II 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 | A | Only Cambridge CXA81 II offers a subwoofer output - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Amplifier class | depends | Cambridge CXA81 II is Class A/B and Arcam A25 is Class G. Class A/B runs warm and is the long-established mainstream choice; Class G/H switches its supply rails to cut the heat a Class A/B design wastes. Modern examples of both measure well - judge by the rest of the page. |
| Price | A | Cambridge CXA81 II costs less - $1,199 against $1,499 at list. |
A Cambridge CXA81 II B Arcam A25
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 CXA81 II is the easier recommendation: it leads on most of the measured areas and costs less. Take Arcam A25 if one of the "depends" rows above describes your system. If you play records, Arcam A25 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.