These are not the same size of amplifier: NAD C 389 has roughly 3.3x the power of NAD C 328. That is about 5.1dB, 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 389 has more power - 130W against 40W into 8 ohms. That is about 5.1dB - a different class of amplifier rather than a bigger version of the same one, and far more than most rooms will ever ask for. |
| Room size | depends | We rate NAD C 328 the better fit for desk or near-field listening and a small room, and NAD C 389 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. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output barely increases (40W and 130W). |
| Noise floor | A | NAD C 328 is the quieter design on paper - 100dB against 95dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board. NAD C 389 goes higher - 384kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Analogue inputs | B | NAD C 389 takes more analogue sources - 3 against 2. |
| Room to grow | evenly matched | The same expansion options on both. |
| Shelf space | depends | NAD C 328 takes up about 21% less shelf area (1349cm² against 1705cm²), and it is 82mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | NAD C 328 costs less - $699 against $1,499 at list. |
| Watts per dollar | B | NAD C 389 is the cheaper watt - about $12 per watt against $17. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A NAD C 328 B NAD C 389
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: NAD C 389 measures better, NAD C 328 costs about 53% 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 - NAD C 389 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 90 watts would be headroom you pay for and never hear - we rate NAD C 389 poorly for near-field use for exactly that reason. Think about the whole system: the roughly $800 saved by taking the cheaper one would buy better speakers or a subwoofer, which does more for the sound than the difference between two competent amplifiers.
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.