Upgrading is an important if not essential part of competition systems.

Car lights dim when the bass hits? The electrical system in most cars is designed to supply power to all the factory-installed components and accessories. If you add power-hungry amplifiers, the car's electrical system can not keep up with the current demands.

Capacitors
The first thing to do is to add a stiffening capacitor. A secondary battery that reacts very quickly to sudden current demands. Stiffening capacitors always help a sound system. Capacitors should be installed as close to the amplifiers as possible, with the positive lead going right into the positive lead of the amp and the ground to a metal part of the car. Capacitors need to be "charged up" first. This is simply done by either putting a resistor or a test light between the positive post of the battery and the positive terminal of the cap. After a few minutes, the capacitor will be charged up, and it can be connected. They are a "patch" for a more serious problem.

High Output Alternators
Another upgrade is a high output alternator and maybe adding a secondary battery (for car off listening) to keep up with higher system's demands.

Additional Batteries
Always keep in mind that when a car is running the batteries become loads that take power away from your amps. A battery isolator should be used to avoid batteries draining each other. Companies such as Optima make batteries that take less power to charge and have a higher output, placing lower demands on an electrical system.