I own a RA820BXII. Brilliant amp which I only replaced a few years ago with an ARCAM A19, and then I only replaced it because the Rotel failed after (was it 30 years) reliable service.
The Musical Fidelity B1 was described by the reviewer in The Gramaphone magazine as "Unnecessarily good .. " An odd thing to say but it was superb. I had one [and a back-up in case of disaster] for 30 years. I would still have it if I didn't need digital inputs.