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 | B | Rotel A12 has more power - 60W against 40W into 8 ohms. That is about 1.8dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate NAD C 328 the better fit for desk or near-field listening, and Rotel A12 for a very large room. Match the amplifier to the room you actually have, not the one you want. |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (100dB vs 100dB). |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Analogue inputs | B | Rotel A12 takes more analogue sources - 4 against 2. |
| Room to grow | evenly matched | The same expansion options on both. |
| Amplifier class | depends | NAD C 328 is Class D and Rotel A12 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 C 328 takes up about 17% less shelf area (1349cm² against 1633cm²), and it is 68mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | A | NAD C 328 costs less - $699 against $800 at list. |
| Watts per dollar | B | Rotel A12 is the cheaper watt - about $13 per watt against $17. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A NAD C 328 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 leads across most of the measured areas for a fairly modest premium, so it is the easier pick if the budget stretches. NAD C 328 is the one to take if it does not.
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.