When you say "Hit Hard" do you mean lots of sub bass or snappy kick drums?
One of the best sounding trucks I have heard had 4 Orion 8's under the back seat facing forward. I was surprised how much bass there was. Best bet would be to remove the back seat, have 3 to 4 10's or 12's facing up for earth moving bass that will most likely drown out your mids and highs but everyone down the block who didn't pay for your system will be able to enjoy it and possibly even remove it from your possession whilst you slept.
OR...... If you are trying to get the most out of the space you have, go with six - 6.5" high excursion subs or four - 8" high excursion subs in some form of ported enclosure.