Sound quality is always a slightly contentious issue as what one person likes may not be the same as another. B&O have in the past had two ranges - the hi-fi range and the audio range.
The Hi-Fi range is where the engineers have been allowed their full rein and these will be comparable with the better of their competitors. Examples are:
Beolab 5000 system of 1967 - expensive at the time and developed to be as good as it could be. Still good today!
Beomaster 3000/4000/4400 - these were the replacement for the 5000 system - not as expensive or quite as well made but very similar performance and the 4400 was exceptional. Regarded by some as the best receiver made by B&O.
Beomaster 8000/6000 - I have put these together but the 6000 is in many ways a 4400 uprated. Not as well built (again!) but good sounding if a little temperamental. The 8000 was a tour de force with B&O throwing everything they knew to make this a powerful and good sounding receiver. Let down by rotten red capacitors (they were fine in their day but have proved to age badly and need replacing , as do those in the 4400) and by some cheaper plastics. None the less, this is a superb receiver.
The audio range included the lesser models such as the 901 and the 1700 etc. nothing wrong with them but built to a price level.
The interesting models are in the middle! Deciding where they go is tricky! The Beomaster 2200 uses similar circuit design, though not construction, to the 4400 and is brilliant, as is the even lower powered BM1500. The 2400 is not as good but is a stunning design! I am not sure I would rate the 4500 that highly on sound either but it is again beautiful.