No single best amplifier here. What decides it is what you have to drive, what you need to plug in, and how much of the system you want in one box.
| Area | Better | Why |
|---|
| Power | A | Hegel H150 has more power - 75W against 40W into 8 ohms. That is about 2.7dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Hegel H150 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 | Hegel H150 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 | The same streaming platforms and services on both. |
| Analogue inputs | A | Hegel H150 takes more analogue sources - 3 against 1. |
| Phono stage | depends | Hegel H150 has a built-in phono stage (MM) 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. |
| Use with a TV | depends | Only Naim Uniti Atom has HDMI ARC, 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 Naim Uniti Atom has a headphone output. Worth something if you listen late, nothing if you never do. |
| Shelf space | depends | Naim Uniti Atom takes up about 48% less shelf area (781cm² against 1505cm²), and it is 34mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Hegel H150 costs less - $3,600 against $3,799 at list. |
| Watts per dollar | A | Hegel H150 is the cheaper watt - about $48 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 Hegel H150 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?
Hegel H150 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 - Hegel H150 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 35 watts would be headroom you pay for and never hear - we rate Hegel H150 poorly for near-field use for exactly that reason. If you play records, Hegel H150 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.