These are not the same size of amplifier: Devialet Expert 140 Pro has roughly 2.6x the power of Naim Uniti Atom. That is about 4.2dB, 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 | A | Devialet Expert 140 Pro has more power - 105W against 40W into 8 ohms. That is about 4.2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Devialet Expert 140 Pro the better fit for a mid-size room, a large room and a very large room, and Naim Uniti Atom for desk or near-field listening and a small room. Match the amplifier to the room you actually have, not the one you want. |
| Speaker load rating | A | Devialet Expert 140 Pro is rated down to 2 ohms against 4, so it is the safer partner for a low-impedance speaker. |
| Built-in DAC | B | Both decode on board. Naim Uniti Atom goes higher - 384kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | evenly matched | Only Naim Uniti Atom has Chromecast. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Analogue inputs | evenly matched | The same number of line-level inputs (1). |
| Phono stage | depends | Devialet Expert 140 Pro has a built-in phono stage (MM,MC) and Naim Uniti Atom 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 | B | Only Naim Uniti Atom offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Headphones | depends | Only Naim Uniti Atom has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Devialet Expert 140 Pro is ADH (Analog Digital Hybrid) and Naim Uniti Atom is Class A/B. Class A/B runs warm and is the long-established mainstream choice. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Naim Uniti Atom takes up about 49% less shelf area (781cm² against 1521cm²), and it is 81mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Naim Uniti Atom costs less - $3,799 against $6,500 at list. |
| Watts per dollar | A | Devialet Expert 140 Pro is the cheaper watt - about $62 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 Devialet Expert 140 Pro B Naim Uniti Atom
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?
Devialet Expert 140 Pro is ahead, but on only 1 of the measured areas, and it costs about 71% more. That is a lot of money for a narrow margin - Naim Uniti Atom is the sensible buy unless a specific feature above decides it for you. 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 - Devialet Expert 140 Pro 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 65 watts would be headroom you pay for and never hear - we rate Devialet Expert 140 Pro poorly for near-field use for exactly that reason. If you play records, Devialet Expert 140 Pro 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.