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 | evenly matched | Effectively the same output - 220W against 235W 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 (340W and 350W). |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (105dB vs 103dB). |
| Built-in DAC | B | Both decode on board, but only Rotel Diamond RA-6000 handles MQA. |
| Streaming | evenly matched | The same streaming platforms and services on both. |
| Use with a TV | depends | Only Michi Prestige X430 has HDMI ARC, 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 | Rotel Diamond RA-6000 costs less - $4,499 against $4,999 at list. |
A Michi Prestige X430 B Rotel Diamond RA-6000
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?
Rotel Diamond RA-6000 has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If this sits under a television, Michi Prestige X430 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.