hu-803 and aftermarker sub!
 

hi ! can anyone give me advice!
i have s60 2002 whit hu-803 and premium sound system with factory amp! i'm happy whit the sound , but just want to add some more bass!
what's the best way to install "12" sub with aftermarker amp!!
i know that i need line converter!
and where do i need to connect it before or after factory amp? and maybe anyone know's wher to get wiring diagramm for my hu-803!!
lot of questions ! but...... everyone is learning!! :confused: thanks!!!