I would agree with Jsloan10 with all the upgrades he stated , Your factory alt should have no problem running the setup you have. The only thing that I would recommend, is rather than installing a capacitor is add another battery instead. The reason why, is that a capacitor is only designed for quick bursts of bass , like you would find in country, rock, classical, dance, etc. If you add a cap to a system that play rap , hip hop, and extreme bass. You actually create another load that your electrical system has to charge. The reason why is , once the capacitor has fully discharged, the bass note is still going. So now not only does the charging system have to supply sufficient voltage to the amplifier to play the note but also to the cap which has to recharge.