If you're gonna do that, then get one 12W7.
Give it LOTS of power.
Can't void warranty unless you supply over 2000 watts RMS at 4ohm.
I heard (a rumor?) that JL hooked the origional prototype of this sub up to 10,000 of clean power at 4ohm and it has been playing some oscilation signal of 20-80HZ since the day it was built and it's still running today.
Wether that's true or not, I heard a car that had just 1 of these and a Rockford Fosgate bd1500 hoowed up to it.... Probably the best sounding bass I've ever heard. Utterly amazing in all respects.
Probably the same money as your 4 sub setup and much more space efficient.
If that's not enough for you,
maybe look at two 10w7's I think they make them.
Quite literally the Ultimate Sub Woofer.
and you'd better have a good sound stage to keep up with them.