These are not the same size of amplifier: Rotel Diamond RA-6000 has roughly 4x the power of Rotel A11 MKII. That is about 6dB, 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 - 200W against 50W into 8 ohms. That is about 6dB - a different class of amplifier rather than a bigger version of the same one, and far more than most rooms will ever ask for. |
| Room size | depends | We rate Rotel A11 MKII the better fit for desk or near-field listening, a small room and a mid-size room, and Rotel Diamond RA-6000 for a large room and a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Speaker load rating | B | Rotel Diamond RA-6000 is rated down to 4 ohms against 8, so it is the safer partner for a low-impedance speaker. |
| 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, but only Rotel Diamond RA-6000 handles MQA. |
| Streaming | evenly matched | Only Rotel Diamond RA-6000 has Roon. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Analogue inputs | evenly matched | The same number of line-level inputs (4). |
| Room to grow | B | Only Rotel Diamond RA-6000 offers preamp outputs and a subwoofer output - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Shelf space | depends | Rotel A11 MKII takes up about 17% less shelf area (1633cm² against 1979cm²), and it is 78mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | Rotel A11 MKII costs less - $799 against $4,500 at list. |
| Watts per dollar | A | Rotel A11 MKII is the cheaper watt - about $16 per watt against $23. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Rotel A11 MKII 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, Rotel A11 MKII costs about 82% less. With most speakers in most rooms that gap is smaller in practice than it looks here. 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, 50 watts is already more than most people ever use, and the extra 150 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. Think about the whole system: the roughly $3,701 saved by taking the cheaper one would buy better speakers or a subwoofer, which does more for the sound than the difference between two competent amplifiers.
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.