if u have it keep it. if its not installed then u don't need it. i have had my system (about 1400 watts total in my ride for almost 2 years on the stock battery and no problems so far.) a cap will help for headlight dimming. i had problems on my old civic with that until i put a cap in. i don't turn on my music loud enuff at night to see my headlights dim now. like someone said up there, a cap stores energy until released, so it will not need a constant charging from the alternator causing more strain on the charging system. it is not needed for a small system but it won't hurt to have it. as for the leds being on it doesn't hurt anything, it takes as much power as an alarms blinking led light