These are not the same size of amplifier: NAD C 399 has roughly 2.4x the power of LEAK Stereo 230. That is about 3.8dB, 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 | NAD C 399 has more power - 180W against 75W into 8 ohms. That is about 3.8dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate LEAK Stereo 230 the better fit for desk or near-field listening, a small room and a mid-size room, and NAD C 399 for a large room and a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | A | LEAK Stereo 230 holds up better into a 4-ohm load: its output increases strongly to 115W, where the other barely increases. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | A | LEAK Stereo 230 is the quieter design on paper - 109dB against 95dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board. LEAK Stereo 230 goes higher - 768kHz against 384kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Analogue inputs | evenly matched | The same number of line-level inputs (2). |
| Room to grow | evenly matched | The same expansion options on both. |
| Amplifier class | depends | LEAK Stereo 230 is Class A/B and NAD C 399 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. |
| Shelf space | depends | LEAK Stereo 230 takes up about 20% less shelf area (1454cm² against 1818cm²), and it is 24mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | LEAK Stereo 230 costs less - $1,695 against $2,899 at list. |
| Watts per dollar | B | NAD C 399 is the cheaper watt - about $16 per watt against $23. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A LEAK Stereo 230 B NAD C 399
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?
LEAK Stereo 230 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - LEAK Stereo 230 is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. 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 - NAD C 399 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 75 watts is already more than most people ever use, and the extra 105 watts would be headroom you pay for and never hear - we rate NAD C 399 poorly for near-field use for exactly that reason.
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.