Both are Rotel, from different ranges - the engineering approach is shared and the differences are mostly in power, connectivity and price.
| Area | Better | Why |
|---|
| Power | B | Rotel RB-1582 MkII has more power - 200W against 130W into 8 ohms. That is about 1.9dB, which is a small step in loudness but real headroom on peaks. |
| Analogue inputs | evenly matched | The same number of line-level inputs (2). |
| Price | A | Rotel RB-1552 MkII costs less - $1,699 against $2,499 at list. |
A Rotel RB-1552 MkII B Rotel RB-1582 MkII
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 is ahead, but on only 1 of the measured areas, and it costs about 47% more. That is a lot of money for a narrow margin - Rotel RB-1552 MkII is the sensible buy unless a specific feature above decides it for you. Think about the whole system: the roughly $800 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.