Spritzer's 009's rankings:
009BK > 009S > 009.
I think Stax stuffed up on the marketing on the 009BK. Surprise to see there a few store that still sell them.
Despite them being the same price as the 009 before they discontinue them.
Considering there only 180 of them show that very very niche market for electrostatic (still a lot of people don't know the technology exist)