What about using a pair of the JBL 5" midrange speakers available on Ebay for less than a hundred a pair? LE5's maybe...they made so many. The crossover could be the same or an Altec. Many were listed as 150 Watts. that would possibly give you some attenuation control as well. The actual power going to the mids would be much less than the low end speakers.
I just bought a trashed Altec 2112 column, took all the hardware, the horn, the speakers and the crossover out and dumped the cabinet. I am playing with the crossover for my JBL 2115 and my 215 bottom. It sounds like it has balanced the highs and lows better than my single cap on the 2115. Plus it has an attenuator.
If I can figure out why my SD card reader died, I'll post the latest pictures...darn computers.