This question is interesting to me. I hope someone will answer.
You may have to post in the General Interest forum to get it seen by someone who knows the answer.

Brian

 My serious build was in High School shop. It was a pair of Speakerlab K horns. As you probably know already, these are rated at 106db per watt. They would likely take 100 watts, at least that is what I fed them, but stick with the 8 ohm impedance. The amps don't care, and the speakers are more than enough capable of giving a huge amount of sound with a watt. The meters on my amps never even moved.
Keep in mind that the bass is also a HORN! It is a folded horn, just like the Klipschorn. 1 watt will move the cone about 1/16", producing bass equal to the volume of the other horns. The distortion will likely be at about 1%. This is not a typo.
I am glad to see that you are upgrading the midrange, as this was the weak spot for these speakers. BTW, if you have never heard bass this powerful, be careful it is NOT like the little boom boom Honda driving by. It is super fast, accurate and very powerful. You will feel it in your chest, and even your pant legs will vibrate. Stick them in a corner first and then experiment. You are never going to hear or forget sound like this.... I never did.