With your setup for using 2 L7 12" SoloBaric definitely you'll need a Capacitor. You've got a heavy duty car audio system with multiple Amps, but the headlights dim every time the bass hits. A capacitors ensure that your system gets a steady supply of power for maximum performance, and acts as a stabilizer between amps and car electrical system. A capacitor stores current for instant release when short bursts of energy needed to produce loud, deep bass notes.
Always remember that to power your speakers and subs, your amplifiers has to draw current from your car electrical system. The higher the wattage of your amps, the more current it needs to draw, and the larger the power cables need to be. Wires that are too small inhibit current flow parang tubo ng tubig na kapag maliit mailiit din ang bigay. So if you want your music flowing loudly and clearly, make sure you wires a big enough to handle your amps demand.