Different price classes - Arcam SA45 costs roughly 2.2x what Rotel RB-1582 MkII 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 | evenly matched | Effectively the same output - 200W against 180W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Amplifier class | depends | Rotel RB-1582 MkII is Class A/B and Arcam SA45 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 | Rotel RB-1582 MkII costs less - $2,499 against $5,500 at list. |
| Watts per dollar | A | Rotel RB-1582 MkII is the cheaper watt - about $12 per watt against $31. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Rotel RB-1582 MkII B Arcam SA45
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 RB-1582 MkII has the edge on paper, though not by much. The rows marked "depends" are more likely to decide this than the score is. Think about the whole system: the roughly $3,001 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.