hey guys.

i want to keep my stock head unit in my '11 HD; i probably won't ever upgrade it.

so, i'm installing a fosgate sub and amp; it needs audio signal to it.

i have two front and two rear door speakers, like all crewcabs.

without disturbing the stock speakers how do i hook up this line output device?
http://www.crutchfield.com/p_161LC2I...62#details-tab

i see the stock speaker wires go into the line controller, then out in the form of rca plugs, then to the speakers. that's easy.
then inside it magically gives me a sub output, which is easy.

do i really need to run the stock wires thru this unit?

i don't want to skimp on the install, wanna right, and if this is the way, then that's fine.

I don't think my radio has a stock sub output.

edit: oh ya, and since it's just a 2 channel line controller, do i take the front or rear speakers thru this device?

thanks,
allen