Small-Medium SUV.
Fords
Explorer
Expedition
Excursion if you can afford 5 gallons to the mile.
Bronco II
Bronco
Bronco with the F-250 cab making it a four door.
Chevrolets
K-5 Blazer
Tahoe
Trail Blazer
More airspace, the sound waves "breathe" through out the entire cabin.
You can fit 4 15"s in the back on an '94 Explorer and still keep it below window line.
I would get a Geo except I'm not to sure on how the fare up when someone smacks into, especially with 4 Big Ass LV4 15's and box behind your head.