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 | evenly matched | Effectively the same output - 60W against 70W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Room size | depends | We rate Technics SA-C600 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. |
| Built-in DAC | B | Both decode on board, but only NAD C 359S handles MQA. |
| Streaming | evenly matched | The same streaming platforms and services on both. |
| Analogue inputs | B | NAD C 359S takes more analogue sources - 3 against 2. |
| Use with a TV | depends | Only NAD C 359S has HDMI eARC, so the television can drive it directly and one remote controls the volume. If the system is for music only, this changes nothing. |
| Room to grow | evenly matched | The same expansion options on both. |
| Built-in sources | depends | Technics SA-C600 has a CD player built in. That is one less box if you still play discs or listen to radio, and dead weight if you do not. |
| Amplifier class | depends | Technics SA-C600 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 | Technics SA-C600 takes up about 33% less shelf area (1161cm² against 1740cm²), and it is 59mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | evenly matched | Priced within a few per cent of each other. |
A Technics SA-C600 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 this sits under a television, NAD C 359S is the one to buy - HDMI ARC means the TV remote controls the volume and there is no second box in the way.
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.