Thinking About 4 12's?

[Jextel]

my current box was built by rich(stratus01 i think thats his username) its alittle more then 4.8 and the subs i was planning on running were the concept's (Basically a RE HC)...Im thinking i should just get a new box built? but i know i wont be able to sell mine(shipping would be a b*tch and ppl around wont pay the amount its worth) so i was wondering should i put them in a seal box or a ported? the lowest space per sub is 1.25 and that will be 5cu..I know for a fact i can get that with alittle more...What to do? thnk i can mod my box

Also this will be in a trunk of a maxima and how do i get close to .5 with 4 dual 2ohm subs?