What are best high end in ear 1 driver and balanced armature ??
Depends on what kind of sound you're looking for and price range...
Phonak, Etymotic, MEE, Westone, as well as others all make (single) BAs, but targetted differently. Even Dunu has a few cheaper BA models.
EDIT: Don't forget ACS also makes the single BA T15s.
I would say a custom re-shelled IEM with a BA that's modified to withstand the entire frequency with more oomph without becoming any more distorted. Maybe a re-shelled ER-4? I would say RE272, but that's dynamic and your title says BA