However at that price, personally I would try something more toward 2 delta 12LF per box with a B&C DE250-8. Definitely not point source however and would probably need a much large box.
Not the same approach but it just seems that 1000 plus dollars opens up some possible viable alternatives for DIY'ers.

Once made a dual delta 12 lf with dual beta 8 and single apt 80 that sounded pretty darn good. [Made for a church.] Perhaps this Great Plains driver is in another league?

Barry