These are not the same size of amplifier: Rotel Diamond RA-6000 has roughly 2.4x the power of NAD M10 V3. That is about 3.7dB, so it is a question of room size and how hard your speakers are to drive, not of one being the better amplifier.
| Area | Better | Why |
|---|
| Power | B | Rotel Diamond RA-6000 has more power - 235W against 100W into 8 ohms. That is about 3.7dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Grip on hard loads | B | Rotel Diamond RA-6000 holds up better into a 4-ohm load: its output increases modestly to 350W, where the other barely increases. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | B | Rotel Diamond RA-6000 is the quieter design on paper - 103dB against 90dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board. Rotel Diamond RA-6000 goes higher - 384kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | A | Only NAD M10 V3 has AirPlay 2 and BluOS. |
| Use with a TV | depends | Only NAD M10 V3 has HDMI, 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. |
| Headphones | depends | Only Rotel Diamond RA-6000 has a headphone output. Worth something if you listen late, nothing if you never do. |
| Amplifier class | depends | NAD M10 V3 is Class D and Rotel Diamond RA-6000 is Class A/B. Class D runs cool and draws almost nothing at idle; 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. |
| Shelf space | depends | NAD M10 V3 takes up about 69% less shelf area (606cm² against 1979cm²), and it is 178mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | NAD M10 V3 costs less - $3,199 against $4,499 at list. |
| Watts per dollar | B | Rotel Diamond RA-6000 is the cheaper watt - about $19 per watt against $32. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A NAD M10 V3 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?
The usual trade-off: Rotel Diamond RA-6000 measures better, NAD M10 V3 costs about 29% less. With most speakers in most rooms that gap is smaller in practice than it looks here. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Rotel Diamond RA-6000 is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. 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, 100 watts is already more than most people ever use, and the extra 135 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.
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.