These are not the same size of amplifier: Buchardt I150 has roughly 2.5x the power of Naim Nait 5si. 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 | B | Buchardt I150 has more power - 150W against 60W 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 Naim Nait 5si the better fit for desk or near-field listening, a small room and a mid-size room, and Buchardt I150 for 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 | Buchardt I150 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 1. |
| Headphones | depends | Only Naim Nait 5si has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Naim Nait 5si is Class A/B and Buchardt I150 is Class D. Class A/B runs warm and is the long-established mainstream choice; Class D runs cool and draws almost nothing at idle. Modern examples of both measure well - judge by the rest of the page. |
| Price | A | Naim Nait 5si costs less - $2,299 against $2,500 at list. |
| Watts per dollar | B | Buchardt I150 is the cheaper watt - about $17 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 Buchardt I150
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: Buchardt I150 measures better, Naim Nait 5si costs about 8% 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 - Buchardt I150 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 90 watts would be headroom you pay for and never hear - we rate Buchardt I150 poorly for near-field use for exactly that reason. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Naim Nait 5si becomes the more rational buy.
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.