These are not the same size of amplifier: PS Audio Stellar Strata MK2 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 | A | PS Audio Stellar Strata MK2 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 PS Audio Stellar Strata MK2 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. |
| Built-in DAC | B | Both decode on board, but only Naim Uniti Atom handles DSD. |
| Analogue inputs | evenly matched | The same number of line-level inputs (1). |
| Phono stage | depends | PS Audio Stellar Strata MK2 has a built-in phono stage 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. |
| Amplifier class | depends | PS Audio Stellar Strata MK2 is Class D and Naim Uniti Atom is Class A/B. Class D runs cool and draws almost nothing at idle; 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 47% less shelf area (781cm² against 1481cm²), and it is 27mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | PS Audio Stellar Strata MK2 costs less - $3,499 against $3,799 at list. |
| Watts per dollar | A | PS Audio Stellar Strata MK2 is the cheaper watt - about $35 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 PS Audio Stellar Strata MK2 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?
PS Audio Stellar Strata MK2 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 - PS Audio Stellar Strata MK2 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 PS Audio Stellar Strata MK2 poorly for near-field use for exactly that reason. If you play records, PS Audio Stellar Strata MK2 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.