Siblings in Arcam's A range, so they share a design and a house sound. It comes down to power, features and price.
| Area | Better | Why |
|---|
| Power | B | Arcam A25+ has more power - 100W against 80W into 8 ohms. That is about 1dB, which is a small step in loudness but real headroom on peaks. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output increases strongly (120W and 165W). |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (106dB vs 106dB). |
| Built-in DAC | B | Both decode on board. Arcam A25+ goes higher - 384kHz against 192kHz. Very few recordings exist above 192kHz, so treat this as headroom, not as sound quality. |
| Analogue inputs | evenly matched | The same number of line-level inputs (3). |
| Use with a TV | depends | Only Arcam A25+ has HDMI eARC, 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 Arcam A25+ is Class G. Class A/B runs warm and is the long-established mainstream choice; Class G/H switches its supply rails to cut the heat a Class A/B design wastes. Modern examples of both measure well - judge by the rest of the page. |
| Price | A | Arcam A15 costs less - $999 against $2,000 at list. |
| Watts per dollar | A | Arcam A15 is the cheaper watt - about $12 per watt against $20. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Arcam A15 B Arcam A25+
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?
Arcam A25+ is ahead, but on only 1 of the measured areas, and it costs about 100% more. That is a lot of money for a narrow margin - Arcam A15 is the sensible buy unless a specific feature above decides it for you. If this sits under a television, Arcam A25+ is the one to buy - HDMI ARC means the TV remote controls the volume and there is no second box in the way. Think about the whole system: the roughly $1,001 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.