So, got the B1 home and compared. Units are identical to each other (including buttons), with the exception that on the new model, the volume pot is thankfully MARKED with a little white dot, though there's no scale. Almost impossible to tell these apart... thank goodness for the dot!
Minimum on the pot is at 8 o'clock and maximum at 6 o'clock. Marked the older model with a marker (barely visible). Tested briefly (and non scientifically) via the FLC 8S (Impedance = 11 Ohm, Sensitivity = 93 dB/mW). On the older model B1, volume was more than adequate at 9 o'clock (so not a lot of play from minimum). On the new model, I got similar volume at 10 o'clock. So that's an improvement. Will do a more thorough comparison in a few days, once I'm done with some reviews of other gear. More to come.