One is a streaming all-in-one and the other is an amplifier. Judge them on how many boxes you want and what you already own, not on the spec sheet alone.
| Area | Better | Why |
|---|
| Power | evenly matched | Effectively the same output - 70W against 80W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Grip on hard loads | A | NAD C 359S holds up better into a 4-ohm load: its output increases strongly to 120W, where the other increases strongly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | B | Cambridge CXA81 II is the quieter design on paper - 105dB against 90dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board. Cambridge CXA81 II goes higher - 384kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | evenly matched | Only NAD C 359S has BluOS. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Analogue inputs | B | Cambridge CXA81 II takes more analogue sources - 5 against 3. |
| Phono stage | depends | NAD C 359S has a built-in phono stage (MM) and Cambridge CXA81 II 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. |
| 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 | B | Only Cambridge CXA81 II offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Price | B | Cambridge CXA81 II costs less - $1,199 against $1,299 at list. |
A NAD C 359S B Cambridge CXA81 II
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?
Cambridge CXA81 II 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 - NAD C 359S 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.