so what to do?
given your budget and blowing past it a bit but with a simple build, i'd suggest:
18 sounds 18lw2400 drivers, 4 ohm version, wired 2 drivers in parallel for 2 ohms net per channel
forward firing ported enclosures, 9 cubic feet each
slot port in each cabinet, 20" wide x 4" high x 20" deep, for a tuning frequency of 30hz
that will give you a system that is about 100db sensitive 1w1m across the bass range.
a cerwin vega amp cv5000 for 5000 watts power.
that will give you about 137db spl 1/2 space or 140+ up against a wall.
it overshoots xmax by some at the very top of the power, but that is fine.
high pass at 30hz, with eq boost at 30hz
low pass at 100hz to mains