[Jumbo Jet]

Running new speaker wire is a snap. You'll run patch cables from the headunit to under the seat (or where ever your amp is), then from out of the amp you'll run your speaker wire to your doors. You can fish the new speaker wire thru the rubber boot in the doors. You'll plug the speaker wire into the crossover of your components, then 2 sets of wires will go out from there. One set to the woofer and the other to your tweeter.

Are you bridging your 4 channel amp to power the sub, or do you have a separate amp for that?