These are not the same size of amplifier: Rotel A12 has roughly 2.4x the power of Rotel DX-5. That is about 3.8dB, 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 A12 has more power - 60W against 25W into 8 ohms. That is about 3.8dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (100dB vs 100dB). |
| Built-in DAC | A | Both decode on board. Rotel DX-5 goes higher - 384kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Streaming | evenly matched | Only Rotel DX-5 has Roon. Neither list is longer in a way that matters - check the one service you actually pay for. |
| Phono stage | depends | Rotel A12 has a built-in phono stage (MM) and Rotel DX-5 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. |
| Room to grow | B | Only Rotel A12 offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Shelf space | depends | Rotel DX-5 takes up about 63% less shelf area (610cm² against 1633cm²), and it is 95mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | Rotel A12 costs less - $800 against $1,699 at list. |
| Watts per dollar | B | Rotel A12 is the cheaper watt - about $13 per watt against $68. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Rotel DX-5 B Rotel A12
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 is the easier recommendation: it leads on most of the measured areas and costs less. Take Rotel DX-5 if one of the "depends" rows above describes your system. 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 A12 has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 25 watts is already more than most people ever use, and the extra 35 watts would be headroom you pay for and never hear. If you play records, Rotel A12 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.