@farukh555
Power amp nay produce karni hay if proper alterntor,battery wiring.Capacitor only helps in storing charge where is required,maintian power,Provide charge where drops.I am using this capacitor this JL 13.5W7,Fusion Nv-am25001 Amplifier,120amp batteries SETUP.Work fine 13.7-14.1v show kata hay works abosultey fine.
And regarding crossfire fire compared to rockfordFosgate,Soundstream you will find the answer on web.