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 - 72W against 60W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Room size | depends | We rate Rega Elex-R the better fit for a mid-size room, a large room and a very large room, and Rotel A12 MKII for desk or near-field listening and a small room. Match the amplifier to the room you actually have, not the one you want. |
| Built-in DAC | B | Rotel A12 MKII has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Analogue inputs | evenly matched | The same number of line-level inputs (4). |
| Room to grow | evenly matched | The same expansion options on both. |
| Shelf space | depends | Rega Elex-R takes up about 16% less shelf area (1376cm² against 1633cm²), and it is 58mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Rotel A12 MKII costs less - $1,100 against $1,395 at list. |
A Rega Elex-R B Rotel A12 MKII
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 A12 MKII has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Rega Elex-R becomes the more rational buy.
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.