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 - 180W against 220W 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 (300W and 340W). |
| Noise floor | A | Arcam SA45 is the quieter design on paper - 110dB against 105dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | A | Only Arcam SA45 has AirPlay 2 and Chromecast. |
| Room to grow | evenly matched | The same expansion options on both. |
| Room correction | A | Arcam SA45 has room correction. In an awkward room that does more for the sound than any other difference on this page. |
| Headphones | depends | Only Michi Prestige X430 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | Arcam SA45 is Class G and Michi Prestige X430 is Class A/B. Class G/H switches its supply rails to cut the heat a Class A/B design wastes; Class A/B runs warm and is the long-established mainstream choice. Modern examples of both measure well - judge by the rest of the page. |
| Price | B | Michi Prestige X430 costs less - $4,999 against $5,500 at list. |
| Watts per dollar | B | Michi Prestige X430 is the cheaper watt - about $23 per watt against $31. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Arcam SA45 B Michi Prestige X430
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 SA45 measures better, Michi Prestige X430 costs about 9% less. With most speakers in most rooms that gap is smaller in practice than it looks here.
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.