Ok the question I have is I want to install a aftermarket amp and sub. I already have a aftermarket hu. Can i just un hook the stock sub and wire the aftermarket sub and amp like a normal car would be wired or do I have to bypass the stock amp. I dont want to run the stock speakers of the aftermarket amp just leave them hooked to the stock amp.

 

Bypass the amp

Run a set of RCA's from the SUB out or REAR out on the back of the HU to the amp.
Run a piece of 16-18 guage wire from the remote out on the HU to the remote on the amp.
Run a fused power wire (guage and fuse size all depend on the amp) to the amp from the + on the battery.
Run a ground (try not to make it any longer than 2 feet) from the amp to a good ground point (sand the paint off at gound location)
Run speaker wire from amp to sub.

It sounds easy when you write it like that, but there are 10 things that are bound to go wrong along the way, just keep a level head and you'll be fine