These are not the same size of amplifier: PS Audio PMG M400 has roughly 2.9x the power of Naim Uniti Star. That is about 4.6dB, 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 PMG M400 has more power - 200W against 70W into 8 ohms. That is about 4.6dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate PS Audio PMG M400 the better fit for a large room and a very large room, and Naim Uniti Star for desk or near-field listening, a small room and a mid-size room. Match the amplifier to the room you actually have, not the one you want. |
| Built-in DAC | B | Naim Uniti Star has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | evenly matched | The same number of line-level inputs (1). |
| Use with a TV | depends | Only Naim Uniti Star 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. |
| Headphones | depends | Only Naim Uniti Star has a headphone output. Worth something if you listen late, nothing if you never do. |
| Built-in sources | depends | Naim Uniti Star has a CD player built in. That is one less box if you still play discs or listen to radio, and dead weight if you do not. |
| Amplifier class | depends | PS Audio PMG M400 is Class A/AB and Naim Uniti Star 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 Star takes up about 24% less shelf area (1371cm² against 1806cm²), and it is 90mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Naim Uniti Star costs less - $5,699 against $8,999 at list. |
| Watts per dollar | A | PS Audio PMG M400 is the cheaper watt - about $45 per watt against $81. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A PS Audio PMG M400 B Naim Uniti Star
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 PMG M400 is ahead, but on only 1 of the measured areas, and it costs about 58% more. That is a lot of money for a narrow margin - Naim Uniti Star 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 - PS Audio PMG M400 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 70 watts is already more than most people ever use, and the extra 130 watts would be headroom you pay for and never hear - we rate PS Audio PMG M400 poorly for near-field use for exactly that reason. If this sits under a television, Naim Uniti Star is the one to buy - HDMI ARC means the TV remote controls the volume and there is no second box in the way.
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.