adding sub to 03 h2 help

not a newbie to the biz just to the board.I'm looking at adding a sub to an 03 h2 for a custome and retaining all the stock bose equipment for some of you gyus that have done this what is the best route to go ? TIA

you have to tap into the speaker wires after the bose amp, all the volume and bass and treble functions are done in the amp, the radio is just a keypad basically, the amp is located in the center console by the factory subwoofer, just tap into the subwoofer wire, can't remember what colors they are, just use a tone generator to find which ones they are, the sub is a dual voice coil so there are going to be two sets of wires going to the sub.

Jazzy