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 | B | Audiolab 9000A has more power - 100W against 60W into 8 ohms. That is about 2.2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Naim Nait 5si the better fit for desk or near-field listening and a small room, and Audiolab 9000A 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 | Audiolab 9000A has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | A | Naim Nait 5si takes more analogue sources - 4 against 3. |
| Phono stage | depends | Audiolab 9000A has a built-in phono stage (MM) and Naim Nait 5si 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 Audiolab 9000A 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. |
| Shelf space | depends | Naim Nait 5si takes up about 14% less shelf area (1300cm² against 1518cm²), and it is 41mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Naim Nait 5si costs less - $2,299 against $2,999 at list. |
| Watts per dollar | B | Audiolab 9000A is the cheaper watt - about $30 per watt against $38. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Naim Nait 5si B Audiolab 9000A
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?
The usual trade-off: Audiolab 9000A measures better, Naim Nait 5si costs about 23% less. With most speakers in most rooms that gap is smaller in practice than it looks here. 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 - Audiolab 9000A has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 60 watts is already more than most people ever use, and the extra 40 watts would be headroom you pay for and never hear - we rate Audiolab 9000A poorly for near-field use for exactly that reason. If you play records, Audiolab 9000A 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.