You wouldn't need to mess with these Kicker crossovers at all. They're JUST for the front tweeters. I'm not sure how adding subs works on a stock system but, I think you end up splicing into the wires going to the rear speakers and adapting them for the subs. ******** does have what you need for all that. Honestly though, a new head unit has sub outputs already built into it and it handles the crossover so, it's practically plug n play. If you're not into what kits are available though then I don't know what else to tell you. Upgrading the speakers and adding a sub is doable and will probably sound ok but, it's far from ideal.
2016 Black 1SS w/ MRC, low-gloss black wheels, auto trans.
1100 - 2/11/2016, 2000 - 3/8/2016, 3000 - 3/9/2016, 3000 w/TPW 4/11 - 3/14/2016, 3100 - 3/28/2016, 3300 - 3/31/2016, 3400 - 4/01/2016, 3800 - 4/09/2016 - VIN: 1G1FF1R74G0169892, 4200 - 4/09/2016, 4B00 - 4/11/2016, 4200 - 4/12/2016, 5000 - 4/13/2016