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 | Naim CI-Uniti 102 has more power - 150W against 100W into 8 ohms. That is about 1.8dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate Arcam A25 the better fit for desk or near-field listening, a small room and a mid-size room, and Naim CI-Uniti 102 for 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 (165W and 260W). |
| Noise floor | B | Naim CI-Uniti 102 is the quieter design on paper - 110dB against 106dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | B | Only Naim CI-Uniti 102 has AirPlay 2 and Chromecast. |
| Analogue inputs | A | Arcam A25 takes more analogue sources - 3 against 1. |
| Phono stage | depends | Arcam A25 has a built-in phono stage (MM) and Naim CI-Uniti 102 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 Naim CI-Uniti 102 has HDMI eARC, 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. |
| Headphones | depends | Only Arcam A25 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Arcam A25 is Class G and Naim CI-Uniti 102 is Class D. Class G/H switches its supply rails to cut the heat a Class A/B design wastes; 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 | Naim CI-Uniti 102 takes up about 43% less shelf area (900cm² against 1580cm²), and it is 64mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | evenly matched | Priced within a few per cent of each other. |
| Watts per dollar | B | Naim CI-Uniti 102 is the cheaper watt - about $10 per watt against $15. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Arcam A25 B Naim CI-Uniti 102
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?
Naim CI-Uniti 102 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If you play records, Arcam A25 saves you buying a phono stage; if you do not, ignore that row entirely. If this sits under a television, Naim CI-Uniti 102 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.