AE TD10M, $ 309
Acoustic Elegance TD10M high efficiency bass/midbass driver
You will have to search hard to find better.
AE TD10M-8 is a very nice driver for a two way speaker in a ported
cabinet to get an F3=60 Hz. It would be a lot of money spent just to
play the 50-300Hz region and in order to properly make a XO point
to a sub, you'd want that kick bass placed in a sealed box with the
right Qtc. Did you have DSP filters in mind?