The best turntable provided by B&O was the Beogram 3000 Type 5210 - mainly because it was a Thorens TD124 Mk2. The bass on these decks is better than anything any other Beogram can provide.
After that, the 4000 series, as Chris mentions, are beautifully made and have a lovely sound. A little bass light but excellent isolation and the cartridges are good. The 8000 range are possibly better but less reliable and nothing like as well made with a fair amount of brittle plastics employed.
Don't forget the radial tracking decks either . The 1700 and decks like the 2200 are very cheap and I think sound just as good as the later tangential decks if not better.