First thing ,
big three improves electrical system in your car , its not the fault of alternator ( output remains same from alternator while only FLOW OF CHARGES is improved )
2nd thing :
Use of Capacitor fails if voltage remains below 11v during playing bass music , dropping voltage below 11v , even amp lost is power and completely starts to distort , if capacitors shows voltage below 11v it , indicates bad charged
mostly it happens drop below 11v , but 10v its comes to more straight failed charged and useless with your system
keep in you mind , putting 2.0f capcitor , you will need to put very big alternator
to charge capacitor rapidly , during Power consumption due to bass by Amplfieir
, thats it ... information about capacitors
and best luck with sale