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 | A | Arcam A15 has more power - 80W against 60W into 8 ohms. That is about 1.2dB, which is a small step in loudness but real headroom on peaks. |
| Room size | depends | We rate Arcam A15 the better fit for a mid-size room, a large room and a very large room, and NAD D 3045 for desk or near-field listening and a small room. Match the amplifier to the room you actually have, not the one you want. |
| Noise floor | A | Arcam A15 is the quieter design on paper - 106dB against 98dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | B | Both decode on board. NAD D 3045 goes higher - 384kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Analogue inputs | A | Arcam A15 takes more analogue sources - 3 against 2. |
| Use with a TV | depends | Only NAD D 3045 has HDMI ARC, 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. |
| Amplifier class | depends | Arcam A15 is Class A/B and NAD D 3045 is Class D. Class A/B runs warm and is the long-established mainstream choice; Class D runs cool and draws almost nothing at idle. Modern examples of both measure well - judge by the rest of the page. |
| Shelf space | depends | NAD D 3045 takes up about 87% less shelf area (208cm² against 1580cm²), and it is 75mm shallower, which is the measurement that decides whether a rack door shuts. |
| Price | B | NAD D 3045 costs less - $899 against $999 at list. |
A Arcam A15 B NAD D 3045
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: Arcam A15 measures better, NAD D 3045 costs about 10% less. With most speakers in most rooms that gap is smaller in practice than it looks here. If this sits under a television, NAD D 3045 is the one to buy - HDMI ARC means the TV remote controls the volume and there is no second box in the way.
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.