its very easy, with the battery in the trunk, just run your power and ground wires to the batt itself, and if you have an aftermarket radio then just run your rca down the side, the trim pannels just pop right up and there is plenty of room inside the factory wire protectors,
if you have the stock head unit then either solder rca ends onto the factory signal wires in the trunk (open trunk and look up in the left corner) or use a Line Output Converter (LOC) between the factory subs and the amp and you will never have to leave the trunk
and repete, WTF are you talking about, using the factory amp to drive real subs, bad F'ing ideal, very low power output, i know your dim, but i hope some lights are still on, i would stick to what you know, demotivational posters!