For SQL I think the w6 is best. I had the older w3 v2 in my Tacoma and while they were good, the w6s were clean and loud.
I don't even have subs in my current car. I think I'm getting old cuz the volume stays low nowadays in my car.
The 12" JL is decent, but I would suggest a pair of 10's. I was looking at a shallow mount 10" for my truck, and happened to be talking to a friend of mine that is a transducer ( speaker ) engineer for Alpine. The SWE-10S4 Type E sub is one he designed, it has a nice flat suspension curve, the motor has a 2.5" coil that can handle some decent power.
The best part is a pair of them wired in parallel will give you a 2 ohm load, and they will install in a sealed box slightly over 1 cubic feet. Linear excursion is listed as 10 mm one way, with a pair of them they should keep up to a single 12" driver with 22mm excursion one way ( displacement of the cone diameter x excursion ). They are fairly shallow depth at 4 3/4".
$ 65 each @ Crutchfield
If you can handle a bit more mounting depth (6"), go for the SWS 10D4, it has 1.5 times more throw (15 mm xmax ). If you shop around, you might find it for less than it lists at Crutchfield. ( Street pricing should be in the $ 90 range ) You would end up with a single 4 ohm load though for the amp with a pair, wire the coils in series on each driver, then connect in parallel. This driver is also designed by my buddy.
With a pair of drivers vs a single driver, you have twice the coil area to dissipate heat, and twice the magnet volume to act as a heatsink, pulling heat away from the coil. The Type E has a tighter gap ( coil to pole piece clearance ) than the Type S. Also, with less coil volume in the gap vs a single longer stroke driver, inductance is less of a problem.
Dual 10" Type S ( SWS 10D4 ) will be within a gnat's hair of a single 12" driver with 22 mm excursion. ( Output ability )