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 | Yamaha A-S801 has more power - 100W against 80W 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 A-S801 the better fit for a large room and a very large room, and NAD C 368 for a small room. Match the amplifier to the room you actually have, not the one you want. |
| Bass control | evenly matched | Similar damping factor (240 vs 300). |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (99dB vs 98dB). |
| Built-in DAC | A | Both decode on board, but only Yamaha A-S801 handles DSD. |
| Analogue inputs | A | Yamaha A-S801 takes more analogue sources - 6 against 2. |
| Room to grow | evenly matched | The same expansion options on both. |
| Amplifier class | depends | Yamaha A-S801 is Class A/B and NAD C 368 is Class D. Class A/B runs warm and is the long-established mainstream choice; Class D runs cool and draws almost nothing at idle. Modern examples of both measure well - judge by the rest of the page. |
| Price | A | Yamaha A-S801 costs less - $900 against $1,199 at list. |
| Watts per dollar | A | Yamaha A-S801 is the cheaper watt - about $9 per watt against $15. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Yamaha A-S801 B NAD C 368
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?
Yamaha A-S801 is the easier recommendation: it leads on most of the measured areas and costs less. Take NAD C 368 if one of the "depends" rows above describes your system.
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.