i actually like the sound of the pioneer shallow mount subs...

installed a bunch of those in hiluxs... sounds great...

i forgot which model... but its does looks like what you are aiming for... i installed 8"s, 10"s and 12"s..

well...its actually a good sounding sub... but factor in the price... actually you could get a lot better... but if you are wiling to pay that price then well.. choice is yours...

sound part.. it cant go as low as normal sub in a bigger enclosure... but if like chest stomping bass... this is a good choice...

and another thing is... i dunno how it would sound with the limited space under your seat... but in my experience... subs if placed too near... you will get the sub bass to be cramped to one spot, audible... this is a possible problem because you hardly could enjoy sub frequency "filling up" the ambiance... i duno about you but i actually find that kind of sound.. weird...