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 - 110W against 90W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output increases strongly (180W and 150W). |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (104dB vs 106dB). |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | A | Only Onkyo Icon A-50 has AirPlay 2, Chromecast and Roon. |
| Use with a TV | depends | Only Onkyo Icon A-50 has HDMI, 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. |
| Amplifier class | depends | Onkyo Icon A-50 is Class A/B and JBL SA550 C is Class G. Class A/B runs warm and is the long-established mainstream choice; Class G/H switches its supply rails to cut the heat a Class A/B design wastes. Modern examples of both measure well - judge by the rest of the page. |
| Price | A | Onkyo Icon A-50 costs less - $1,600 against $1,999 at list. |
| Watts per dollar | A | Onkyo Icon A-50 is the cheaper watt - about $15 per watt against $22. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Onkyo Icon A-50 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?
Onkyo Icon A-50 is the easier recommendation: it leads on most of the measured areas and costs less. Take JBL SA550 C if one of the "depends" rows above describes your system. If this sits under a television, Onkyo Icon A-50 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.