My concern is the lowest x-over frequency. Right now, 60 Hz is the choice.
Below 60 Hz will ultimately be infinite baffle bass. No concern there. Where I am purplexed at is my choice of mid-bass. I was leaning towards building a reaction cancelling mid bass horn; I want the impressive dynamic slam of a horn system. Obviously, a problem is that at 60 hz a horn would have to be quite large. Actually, I can make the mouth exit size large enough, it's the length required that bothers me. If I move the x-over frequency to 80, I'm afraid I will be feeding too much of the "slam" range to the subs. My other alternative is to scrap the mid horn idea, and to replace it with 4x 12" pro drivers for mid-bass (per channel).

Just for reference, the other two crossover frequencies will be 250 and 3K.
All active system.

Thanks.