i just bought a MAssive 2 Farad cap from Radio Shack for 49.99 + tax. When the car is running the digital meter on it usually never goes below 13.5 and usually stays up around 14-15. It made my system SOOO much louder, almost stopped headlilght dimming completely! and I have two amps running off it. One Punch 325.1 running 2 Punch stage 1 subs wired in four ohms, so each sub is splitting 408W RMS. Then I have my pioneer 6x9's running off of a 170RMS SPL amp.