Sealed or ported?= costom ported8's,10's,12's,15's ?= 15 or 18
Single sub or mutiple subs?= single
How much room is there to work with?= lots
What kind of wattage do we have to work with?= 1800 (a 4000 watt RMS woofer is not going to be very musical)
So a single 15 to 18 inch woofer in the back of an SUV that can handle 1800 watts RMS and is musical.
In this range you would need to either need a very shitty woofer or bad enclosure to not hit hard.
Suggested companys-
Eclipse
Reasonant engineering
Atomic
Digital Designs
Treo
Ascendant audio
MTX
Earthquake
Alpine
Ground zero engineering
Memphis
Kicker
Power acoustic
Elevation audio
Incriminator audio
Vids of these companys subs here-
http://www.realmofexcursion.com/videos.html