Different price classes - Arcam A5+ costs roughly 2.4x what Rotel A8 does. Expect it to lead on paper; the question is whether you will hear the difference through the speakers you own.
| Area | Better | Why |
|---|
| Power | B | Arcam A5+ has more power - 50W against 30W into 8 ohms. That is about 2.2dB, so it plays usefully louder before it runs out and has more in hand on peaks. |
| Grip on hard loads | B | Arcam A5+ holds up better into a 4-ohm load: its output increases strongly to 75W, where the other increases modestly. That matters with demanding speakers far more than the 8-ohm figure does. |
| Noise floor | B | Arcam A5+ is the quieter design on paper - 106dB against 90dB. Audible mainly with sensitive speakers in a quiet room. |
| Built-in DAC | evenly matched | Both have a DAC on board with much the same capability. |
| Room to grow | B | Only Arcam A5+ offers preamp outputs - which decides whether you can add a subwoofer or a power amplifier later without replacing the box. |
| Price | A | Rotel A8 costs less - $499 against $1,200 at list. |
| Watts per dollar | A | Rotel A8 is the cheaper watt - about $17 per watt against $24. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Rotel A8 B Arcam A5+
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 A5+ measures better, Rotel A8 costs about 58% less. With most speakers in most rooms that gap is smaller in practice than it looks here. If your speakers are a difficult load - 4 ohms nominal, big woofers, or a sensitivity in the low 80s - Arcam A5+ is the safer partner, because how an amplifier behaves when the impedance drops matters more than its 8-ohm rating. 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 - Arcam A5+ has the headroom, and headroom is what stops an amplifier hardening up on peaks. At desk distance or in a small room, 30 watts is already more than most people ever use, and the extra 20 watts would be headroom you pay for and never hear.
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.