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 | A | Arcam SA30 has more power - 130W against 90W into 8 ohms. That is about 1.6dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate Arcam SA30 the better fit for a large room and a very large room, and JBL SA550 C for a small room. Match the amplifier to the room you actually have, not the one you want. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output increases strongly (200W and 150W). |
| Noise floor | A | Arcam SA30 is the quieter design on paper - 112dB against 106dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | A | Both decode on board, but only Arcam SA30 handles MQA. |
| Streaming | A | Only Arcam SA30 has AirPlay 2, Chromecast and Roon. |
| Analogue inputs | A | Arcam SA30 takes more analogue sources - 4 against 3. |
| Use with a TV | depends | Only Arcam SA30 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. |
| Price | B | JBL SA550 C costs less - $1,999 against $3,300 at list. |
A Arcam SA30 B JBL SA550 C
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?
The usual trade-off: Arcam SA30 measures better, JBL SA550 C costs about 39% less. With most speakers in most rooms that gap is smaller in practice than it looks here. If this sits under a television, Arcam SA30 is the one to buy - HDMI ARC means the TV remote controls the volume and there is no second box in the way. Think about the whole system: the roughly $1,301 saved by taking the cheaper one would buy better speakers or a subwoofer, which does more for the sound than the difference between two competent amplifiers.
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.