Couple of things to note:
1) If your looking at peak power on anything your doing it wrong.
2) If your wasting your money on a capacitor your also doing it wrong.
u need a cap if your pushing over 1000 watts. as well as a new alternator. and peak power is just as helpful as rms simply for hard hitting songs. if your amp has a lower peak rating than the subs you wont get the full potential from the subs. if the subs suck too much energy they will shut off. and if your running a cheap amp u can blow the amp and subs.
2000 v6 mustang RED: Totaled
2002 Mustang GT Convertible SILVER:
MGW short throw shifter, 4.10 gears, Bama Performance tuner, Airaid CAI, Bassani off-raod x-pipe, Borla Stinger Catback, Athracite FR500's (275 front, 315 rear), Bilstein shocks/struts, H&R lowering springs, Maximum Motorsport cc plates, Mach 1 chin spoiler, shorty antenna,