hi

i have had no probs with filter as for more power erm cant realy tell but sounds great

as for ya stereo i run 3 amps 2 12" subs and dont have a problem with charge system

as for the last question erm


sounds like some one has fitted an fm modulator thats what the switch may be for they are used so you can have an input from cd dvd, video player and so on this is a shot in the dark you will have to trace where they go to,as for the jack plug no idea

hope this helps