Out of those two, Id prob go for the 12,giving some room to place your amps,and hopefully not rattle your undeadened vehicle as much as the 15, in which will take up more space/possibly all of the trunk space,and be sure to get roadside assistance in case you have a flat,cause its gonna be a PITA to get to that spare tire at that point either way..lol,.But i think you can make a better well speced enclosure for the 12 verses the 15 in my opinion in that vehicle..my neighbor has one of those cars.