X2. We installed 4 10 SSi's under the rear seat of a Ford crew cab. We feed them 4k and ended up having to reinforce the floor it was literally f+cking the truck up. Very very loud, everyone that took a listen was all over it to make sure it was not a blow through.going under the seat in a ford supercab so have to keep the mounting depth short. i had a ssi 10 in there but the pole shifted in the magnet so i need a new magnet. i havnt found a sub that will play like the ssi on 1000 watts and still stay under 5.25 in mountin depth