about the B1 active XO's. There's really not much to say. Any active filter that uses an opamp as a buffer (I.e. where output is directly tied to the '-' input) AND a cap blocks DC from the output to the feedback loop should be able to use a B1 like buffer. The circuits in sections 1, 2, 3 and 7 of SL's filter page
all qualify, but the rest may be sketchy in my mind since the B1 can have some DC offset.
Attached is a rough drawing I scribbled last night for my own benefit, so it ain't pretty. An input buffer is something I'm still debating needing or not, but I'm leaving some room for it.
I'm going to let Soundeasy help me define the values, but the drivers are pretty well behaved in their desired bandwidth such that nearly textbook filters can be used.
I don't have enough JFETs of any one type for everything, so I'm going to have to mix types, probably LSK170s for the woofer and Toshi 2SK170s for the mid/tweet.