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 | B | NAD C 359S has more power - 70W against 55W into 8 ohms. That is about 1dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate Yamaha WXA-70A the better fit for desk or near-field listening and a small room, and NAD C 359S 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 | A | Yamaha WXA-70A holds up better into a 4-ohm load: its output nearly doubles to 105W, where the other increases strongly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | evenly matched | The same streaming platforms and services on both. |
| Analogue inputs | B | NAD C 359S takes more analogue sources - 3 against 1. |
| Phono stage | depends | NAD C 359S has a built-in phono stage (MM) and Yamaha WXA-70A 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 Yamaha WXA-70A offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Headphones | depends | Only NAD C 359S has a headphone output. Worth something if you listen late, nothing if you never do. |
| Shelf space | depends | Yamaha WXA-70A takes up about 66% less shelf area (587cm² against 1740cm²), and it is 133mm 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 | B | NAD C 359S is the cheaper watt - about $19 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 Yamaha WXA-70A 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?
NAD C 359S 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 - Yamaha WXA-70A is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. 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.