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 | Onkyo Icon A-50 has more power - 110W against 80W into 8 ohms. That is about 1.4dB, which is a small step in loudness but real headroom on peaks. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output increases strongly (180W and 120W). |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (104dB vs 105dB). |
| Built-in DAC | A | Both decode on board. Onkyo Icon A-50 goes higher - 768kHz against 384kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | A | Only Onkyo Icon A-50 has AirPlay 2, Chromecast and Roon. |
| Phono stage | depends | Onkyo Icon A-50 has a built-in phono stage and Cambridge Audio CXA81 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. |
| Room to grow | B | Only Cambridge Audio CXA81 offers a subwoofer output - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Price | B | Cambridge Audio CXA81 costs less - $1,499 against $1,600 at list. |
| Watts per dollar | A | Onkyo Icon A-50 is the cheaper watt - about $15 per watt against $19. 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 Cambridge Audio CXA81
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 leads across most of the measured areas for a fairly modest premium, so it is the easier pick if the budget stretches. Cambridge Audio CXA81 is the one to take if it does not. If you play records, Onkyo Icon A-50 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.