These are not the same size of amplifier: Primare I25 has roughly 2.5x the power of Naim Uniti Atom. That is about 4dB, 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 | Primare I25 has more power - 100W against 40W into 8 ohms. That is about 4dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Naim Uniti Atom the better fit for desk or near-field listening and a small room, and Primare I25 for a mid-size room, a large room and a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Built-in DAC | A | Naim Uniti Atom has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Streaming | A | Only Naim Uniti Atom has Chromecast and Roon. |
| Analogue inputs | B | Primare I25 takes more analogue sources - 5 against 1. |
| Room to grow | evenly matched | The same expansion options on both. |
| Headphones | depends | Only Naim Uniti Atom has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Naim Uniti Atom is Class A/B and Primare I25 is Class D. Class A/B runs warm and is the long-established mainstream choice; 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 Uniti Atom takes up about 60% less shelf area (781cm² against 1970cm²), and it is 140mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Primare I25 costs less - $3,295 against $3,799 at list. |
| Watts per dollar | B | Primare I25 is the cheaper watt - about $33 per watt against $95. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Naim Uniti Atom B Primare I25
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?
Primare I25 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. 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 - Primare I25 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 40 watts is already more than most people ever use, and the extra 60 watts would be headroom you pay for and never hear - we rate Primare I25 poorly for near-field use for exactly that reason. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Primare I25 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.