Your stock electrical charging system was designed and built for the stock features of your car.
Whether you need a second battery for car audio is determined by your application and by how much power your amplifiers are using.
Relying on a stock electrical system for the massive amperage that car audio amplifiers require, while still supplying your vehicle with the current it needs will result in low voltage and other problems.
High Output Alternators increase the amperage of your system.
To think about it like water pressure: If your wiring is a straw that allows for 100 PSI, and your car uses 90-95 PSI, there isn’t much pressure left in the straw for your amp. This will result in poor performance, amplifiers illuminating the dreaded red light, and headlight dimming.
Your ground wire is crucial. It can save or destroy your system, so it's important to get this step right.
You'll want to set your ground wire as close to your amplifier as popular, using the same gauge wire as your power wire.
Q-Mat dampens vibrations in your car before they reach your vehicle’s panels by absorbing the shock of the sound waves. Reducing the vibration the sheet metal receives keeps your panels right in place.