the amps arent actually different voltages, that is just what the company uses to test the amps and show you the ratings for. so an amp that says 150 watts at 12v is actually more powerful then an amp that says 150 watts at 14.4 so lok for an amp that makes a good rms power at the lower volts when your car is running it puts out 14.4 a lot and a cap can help raise it.
HU: Pioneer Premier P-720
Front: JVC 2 way 6.5" component system
Rear: Kenwood KFC-1687
Subs: (2) 2002 Kicker 15" L7's
Amps: (2) Infinity Beta Digital 300's
(2) 1 farad Stinger Power Caps
(2) 1 farad Monster Cable Monster Caps