First, good for you for realizing the value and quality of Yamaha basses. They are magnificent and often under-appreciated instruments.
I use a BB400, a BB434, a BB450 (all fretted), and a BB3000af (fretless), all bought used. Each of them is an outstanding instrument in its own way. The BB3000 is the only active one of the bunch, but there's no way I would call it orders of magnitude better than the others just because of its bigger number. They're all just wonderful basses.
Do you know about the "Vintage Yamaha Basses" group on Facebook? Lots of really smart people there who can probably answer your question with much more authority than I. But I have to say that I'm absolutely loving my latest acquisition -- the BB434 -- which I bought "distressed" on Ebay. As usual, Yamaha did lots of things right with that new BB series.
Last I knew, there was a pretty much brand-new BBP34 for $925 ($1500 new) and a BB3000 ($1100, I think) for sale right here on TB Classifieds. Both look like really good deals. Good luck.