To really highlight the bass of your car stereo, you need a setup capable of properly reproducing low frequency notes. You can take the speaker leads off the back of the stock stereo and route them directly to your amp. Adding an amp and subwoofer to a stock radio can be the easiest way to improve your stereo system in your car, if you do it correctly. How should I connect the remote wire so that I don't have to disconnect it when I turn off the car? Its ratings are: Unless you can get a full range signal behind the head unit you should get your signal at the stock sub. Share the knowledge!
Have you considered maybe the quality of the product is not up to par?
Installing Subwoofers in a Car
No other factory wiring need be interfaced other than the accessory wire on the stock radio, used to activate the new amplifier when the stereo is turned on. The RMS is also the amount of power the amplifier can continuously put out without over heating. Check this out - it's a bundle, has everything you should need to do the job. It has a Harmon Carmen premium system. Run the majority of the power cable through the hole in the firewall, making sure to leave enough wire to get to the battery.