No single best amplifier here. What decides it is what you have to drive, what you need to plug in, and how much of the system you want in one box.
| Area | Better | Why |
|---|
| Power | A | Bluesound POWERNODE N331 has more power - 100W against 70W into 8 ohms. That is about 1.5dB, which is a small step in loudness but real headroom on peaks. |
| Noise floor | A | Bluesound POWERNODE N331 is the quieter design on paper - 102dB against 90dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board, but only Bluesound POWERNODE N331 handles DSD. |
| Streaming | evenly matched | The same streaming platforms and services on both. |
| Analogue inputs | B | NAD C 359S takes more analogue sources - 3 against 2. |
| Phono stage | depends | NAD C 359S has a built-in phono stage (MM) and Bluesound POWERNODE N331 does not. Decisive if you own a turntable, completely irrelevant if you do not - and an outboard phono stage is easy to add later either way. |
| Room to grow | A | Only Bluesound POWERNODE N331 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Amplifier class | depends | Bluesound POWERNODE N331 is Class D and NAD C 359S is Class A/B. Class D runs cool and draws almost nothing at idle; Class A/B runs warm and is the long-established mainstream choice. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | Bluesound POWERNODE N331 takes up about 76% less shelf area (418cm² against 1740cm²), and it is 210mm 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 | Bluesound POWERNODE N331 is the cheaper watt - about $13 per watt against $19. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Bluesound POWERNODE N331 B NAD C 359S
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?
Bluesound POWERNODE N331 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If you play records, NAD C 359S saves you buying a phono stage; if you do not, ignore that row entirely.
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.