TRYING TO HOOK UP SOME SUBS WITH A STOCK UNIT BUT IT WONT WORK HELP!!!

HEY GUYS IM NEW HERE BUT IM TRYING TO HOOK UP SOME KICKERS TO MY A6. I BOUGHT ONE OF THOSE MOD THINGS THAT GIVE ME RCA OUTPUTS BUT I TRIED TO HOOK IT...

I added a 12 inch boxed sub to my Bose system. I didn't bother with adding the RCA leads. Ran a new power wire straight from the battery. You can splice the blue P con wire off the amp in the back, and spliced into the speaker wires in the small stock sub for my leads. The added bass was worth the effort.