I was just looking for ideas about adding a sub in an under seat enclosure while keeping all installed stock audio equipment. I believe I will need an amp & sub. I already have an enclosure. Any thing else I'll need or things I need to consider? I'm not interested in show quality sound, just great sound while driving to-and-from work. Thanks.

 

Well i personally have not heard what a sub sounds like under the seat, but you will need an amp and sub. One of the bad things about putting the sub under your passenger seat, is you use a perfect spot for an amp. But you can always put the amp under the drivers side seat and move your jack to the rear comparment. Just make sure you get an amp that will fit under the seat and you match the amps power with what the sub can handle. Once this is all done you will still look stock, because everything will be hidden. Good luck.
P.S. You will need a power kit(power wire, remote wire and ground wire), RCA's and a line level converter(turns speaker output from radio to rca outputs).