No single best amplifier here. What decides it is what you have to drive, what you need to plug in, and how much of the system you want in one box.
| Area | Better | Why |
|---|
| Power | B | Yamaha WXA-50 has more power - 55W against 30W into 8 ohms. That is about 2.6dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Room size | depends | We rate Rega io the better fit for desk or near-field listening, and Yamaha WXA-50 for a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Built-in DAC | B | Yamaha WXA-50 has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | A | Rega io takes more analogue sources - 2 against 1. |
| Phono stage | depends | Rega io has a built-in phono stage (MM) and Yamaha WXA-50 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 Yamaha WXA-50 offers preamp outputs and a subwoofer output - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Headphones | depends | Only Rega io has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Rega io is Class A/B and Yamaha WXA-50 is Class D. Class A/B runs warm and is the long-established mainstream choice; Class D runs cool and draws almost nothing at idle. Modern examples of both measure well - judge by the rest of the page. |
| Price | B | Yamaha WXA-50 costs less - $599 against $725 at list. |
| Watts per dollar | B | Yamaha WXA-50 is the cheaper watt - about $11 per watt against $24. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Rega io B Yamaha WXA-50
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?
Yamaha WXA-50 is the easier recommendation: it leads on most of the measured areas and costs less. Take Rega io if one of the "depends" rows above describes your system. Start with the room. In a large or open-plan room, or with speakers that are hard to drive - low sensitivity, or an impedance that dips - Yamaha WXA-50 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 30 watts is already more than most people ever use, and the extra 25 watts would be headroom you pay for and never hear. If you play records, Rega io 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.