These are not the same size of amplifier: Primare I25 Prisma 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 Prisma 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 Prisma 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 | B | Both decode on board. Primare I25 Prisma goes higher - 768kHz against 384kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | evenly matched | Only Primare I25 Prisma has AirPlay 2. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Analogue inputs | B | Primare I25 Prisma 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 Prisma 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 | A | Naim Uniti Atom costs less - $3,799 against $4,495 at list. |
| Watts per dollar | B | Primare I25 Prisma is the cheaper watt - about $45 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 Prisma
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 Prisma leads across most of the measured areas for a fairly modest premium, so it is the easier pick if the budget stretches. Naim Uniti Atom is the one to take if it does not. 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 Prisma 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 Prisma poorly for near-field use for exactly that reason.
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.