I look forward to hearing what you think of you BA4's when you get them.
I'm going to take my time deciding which model to get next, but it'll be something bass/mid centric.
I've been trying some online tone sweeps and the YH-TF10 seems to make sounds audible right down to 20 Hz, maybe even 18 depending on which generator I use.
The you-tube generators seem pretty useless though, some seem to suggest that sound is audible down to 4-5 Hz!, which can't be right at all.
There are frequency charts that suggest the TF10's are able to produce tones down to 10Hz. They may well be able to, but what they can't do is produce low bass with any impact, I don't think this is a particular limitation of the TF10's, pretty much most BA drivers struggle with low bass extension.
I, like you, have eclectic musical tastes and I was looking for the TF10 with the added dynamic to be able to produce the bass extension AND impact that some modern forms of music require. Hopefully, what you have got with your added dynamic now, is both the bass extension and the actual impact that goes with that extension. Certainly the dynamic should be able to do that far better than the BA could.