Ok i have a question about a cap i need?

my sub rms is 750 so is my amp.....and ever since i got my gain and crap tuned up real good my headlights dim like s**t....also ever since i got my front and rear speakers installed......and since i dont got about 1000 watts i know i need like a 1 farad cap....but would it hurt to hook up a 2 farad cap up to it....im going to hook it up to my sub amp not my 4 channel