Using the stock receiver? If so I would recommend ditching the factory amp and installing a line driver and running RCAs from there to your amp. Most people use a LOC from the rear 6x9's to their sub amp but those speakers only receive a certain frequency range (to make up for the poor quality of the factory speaker) and will leave many low notes sounding muddy.
I still haven't decided if i'm going to keep the stock receiver, maybe in the future I'll replace it. So would a LOC still be useful in an aftermarket unit? Also I plan on running new 12ga for everything.
And honestly I would ditch the 6x9s. Even if you throw a full range signal at them via an aftermarket amp they won'd do much for you besides rattle the ever loving shit out of the rear deck.
I am seriously considering taking them out, but IF I replaced them with 10" subs wouldn't that also rattle my car?
What I did:
Factory receiver - spliced the front 2 channels on the factory amp INPUT harness to a rockford fosgate line driver. From there ran some RCAs to my rear JL 500/1 amp, and then RCAs from that amp to my JL 300/4 amp.
For speaker wires I wanted to run new wire to the doors but I ran short on time so I ran my speaker wires from the JL 300/4 up the center console and spliced them back into each channel of the factory amp OUTPUT harness.
My set up is Focal 165A1 SG comps front and rear powered by a JL slash 300/4 and a JL 12w6 powered by a JL slash 500/1.
Since my remote wire is powered via regular 12 volt power and not a remote turn on via an aftermarket head unit I also installed a delay turnon module for the amps to prevent power on pops which fried my previous JL 12w6 (learned the hard way)
Wow I did not know that.I'm not if this is the right product or how many seconds I should delay it https://www.amazon.com/Delay-Relay-B...turn+on+module
Also installed PLENTY of 80mil thick sound deadening material to the doors, trunk, rear deck, everywhere I could really. Made the mids sound much warmer and less "tinny."
I bought 3 packs of 36 sq ft. of NOICO 80 mil sounds deadener. In hot Texas heat and with the roller it was very easy to install. I'm going to be apply it everywhere I can