Thanks for all the help, Wayne.

Last week, I used foobar 2000's DSP filter plugin to test various filter types / x-over points and slopes . There didn't seem to be much difference (if any) between a 4KHz and 5 KHz point, so I picked 5KHz as the higher x-over point allows the tweeters to play louder with less distortion.

I've ordered parts for a 5KHz / 3rd order filter and a zobel ciruit for the open baffle woofer array . Rather than use a passive filter to tame the mid-bass / mid-range hump, I plan to use the eq. in foobar 2000 for this purpose, if I eventually find it an issue. The tweeter impedance peak is fairly benign (2 ohm above the nominal 6 ohms).

Almost there.