how to reduce headlight dimming for 06 cobalt with a sound system?

[bballtm4224]

I have a 06 cobalt LT with a system in it about 1600 watts total with the 2 amps...i have a yellow top optima and a 1800 kenetik cell battery and the head lights still dim along with the speedomter lights...how can i fix this new alternator?