I would like to make clear that I have no experience with any of these.
I have shopped for drivers long and hard and noticed the P-Audio PA-D45 and BM-D450 looked like good candidates for a 2370 horn.

The B&C also has frequency resonse that looks complimentary to 2370, but has a reccomended range of operation starting at 2,200 Hz and a bottom limit listed at 1,500 Hz. I would be afraid that you would be running the driver at resonance with a 1.6 Khz x-over (Fs isn't listed for the B&C). On a horn designed for 650 Hz, or with a Pi x-over (1600 Hz) I like lower Fs. I also wonder about the sound or the mylar diaphragm on the B&C as versus titanium.

At 1600 Hz x-over the cuttoff of the horn and the resonance of the driver are both more than an octave away. This is said to be the best situation, and should push throat distortion and resonance issues out of range. On paper this combo is a very good fit! A nice bonus with low Fs and horn cuttoff, you could cross over a bit lower if you wanted to (especially in home use), making even more woofers a viable match.

Keep in mind I am an amatuer and this is just an armchair assesment.

Let us know what happens, It's real cool when people find a way to do the Pi thing where "standard" parts are not always available.
Thomas