it will be a somewhat of a bitch to do though because they don't leave a whole lot of slack at the plug on the deck speakers. Obviously power and ground will be a piece of cake
this is what I'm planning to use to get the signal from the rear speaker to the sub. http://www.audiocontrol.com/car-audio/factory-system-upgrade/lc2i/
i have a simple LOC. I dont need that expensive LOC or its post processing of the signal. Tapping into the wires are a cinch.
Somewhere i probably stil have a simple loc also but for my system the lc2i is better because it makes up for the factory bass cutoff2at higher volume.
it can only amply or fix what its getting fed. soo im sure its about the same. It will sound weird. Im just going to tap of the same place i did in the ram. the factory sub. Its already being fed low tones