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 - 90W against 80W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Grip on hard loads | A | JBL SA550 C holds up better into a 4-ohm load: its output increases strongly to 150W, where the other barely increases. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | A | JBL SA550 C is the quieter design on paper - 106dB against 84dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board, but only NAD C 700 handles MQA. |
| Streaming | B | Only NAD C 700 has AirPlay 2, Roon and BluOS. |
| Analogue inputs | A | JBL SA550 C takes more analogue sources - 3 against 2. |
| Phono stage | depends | JBL SA550 C has a built-in phono stage (MM) and NAD C 700 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 700 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 NAD C 700 offers a subwoofer output - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Headphones | depends | Only JBL SA550 C has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | JBL SA550 C is Class G and NAD C 700 is Class D. Class G/H switches its supply rails to cut the heat a Class A/B design wastes; Class D runs cool and draws almost nothing at idle. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | NAD C 700 takes up about 58% less shelf area (651cm² against 1565cm²), and it is 51mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | NAD C 700 costs less - $1,599 against $1,999 at list. |
A JBL SA550 C B NAD C 700
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?
Neither runs away with it - they trade advantages. Let the "depends" rows and the speakers you already own settle it. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - JBL SA550 C is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. If you play records, JBL SA550 C 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.