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 | B | Rotel Diamond RA-6000 has more power - 235W against 140W into 8 ohms. That is about 2.2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output increases strongly (220W and 350W). |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (103dB vs 103dB). |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | A | Only Rotel RAS-5000 has AirPlay 2 and Chromecast. |
| Analogue inputs | B | Rotel Diamond RA-6000 takes more analogue sources - 4 against 1. |
| Phono stage | depends | Rotel Diamond RA-6000 has a built-in phono stage (MM) and Rotel RAS-5000 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. |
| Use with a TV | depends | Only Rotel RAS-5000 has HDMI eARC, 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 | A | Rotel RAS-5000 costs less - $2,999 against $4,499 at list. |
A Rotel RAS-5000 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 is ahead, but on only 1 of the measured areas, and it costs about 50% more. That is a lot of money for a narrow margin - Rotel RAS-5000 is the sensible buy unless a specific feature above decides it for you. 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 - Rotel Diamond RA-6000 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 140 watts is already more than most people ever use, and the extra 95 watts would be headroom you pay for and never hear - we rate Rotel Diamond RA-6000 poorly for near-field use for exactly that reason. If you play records, Rotel Diamond RA-6000 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.