Siblings in Arcam's SA range, so they share a design and a house sound. It comes down to power, features and price.
| Area | Better | Why |
|---|
| Power | A | Arcam SA45 has more power - 180W against 120W into 8 ohms. That is about 1.8dB, 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 (300W and 200W). |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (110dB vs 110dB). |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Streaming | evenly matched | The same streaming platforms and services on both. |
| Room to grow | evenly matched | The same expansion options on both. |
| Price | B | Arcam SA35 costs less - $3,300 against $5,500 at list. |
A Arcam SA45 B Arcam SA35
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 SA45 is ahead, but on only 1 of the measured areas, and it costs about 67% more. That is a lot of money for a narrow margin - Arcam SA35 is the sensible buy unless a specific feature above decides it for you. Think about the whole system: the roughly $2,200 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.