These are not the same size of amplifier: NAD C 389 has roughly 2.6x the power of NAD C3030. That is about 4.1dB, 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 50W into 8 ohms. That is about 4.1dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output barely increases (50W and 130W). |
| Noise floor | B | NAD C 389 is the quieter design on paper - 95dB against 90dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Room to grow | B | Only NAD C 389 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Shelf space | depends | NAD C3030 takes up about 29% less shelf area (1208cm² against 1705cm²), and it is 54mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | NAD C3030 costs less - $1,199 against $1,499 at list. |
| Watts per dollar | B | NAD C 389 is the cheaper watt - about $12 per watt against $24. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A NAD C3030 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?
NAD C 389 leads across most of the measured areas for a fairly modest premium, so it is the easier pick if the budget stretches. NAD C3030 is the one to take if it does not. 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, 50 watts is already more than most people ever use, and the extra 80 watts would be headroom you pay for and never hear - we rate NAD C 389 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.