Both are NAD, from different ranges - the engineering approach is shared and the differences are mostly in power, connectivity and price.
| Area | Better | Why |
|---|
| Power | A | NAD C 389 BluOS-D has more power - 130W against 100W into 8 ohms. That is about 1.1dB, which is a small step in loudness but real headroom on peaks. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output barely increases (130W and 100W). |
| Noise floor | A | NAD C 389 BluOS-D is the quieter design on paper - 95dB against 90dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board. NAD C 389 BluOS-D goes higher - 384kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | evenly matched | The same streaming platforms and services on both. |
| Room to grow | evenly matched | The same expansion options on both. |
| Headphones | depends | Only NAD C 389 BluOS-D has a headphone output. Worth something if you listen late, nothing if you never do. |
| Shelf space | depends | NAD M10 V3 takes up about 67% less shelf area (606cm² against 1809cm²), and it is 138mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | evenly matched | Priced within a few per cent of each other. |
| Watts per dollar | A | NAD C 389 BluOS-D is the cheaper watt - about $20 per watt against $25. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A NAD C 389 BluOS-D B NAD M10 V3
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 BluOS-D has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is.
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.