dimming lights

Ok guys I have a 2000 jimmy v-6 with stock alternator if that helps. My battery is ac delco 810, 650 cold cranking amps. Then I have a jl aduio 500/1 and a 300/4. My lights are dimming if i turn up the sub so should IA. buy and optima yellow top b. try a new alternatorc. capacitor

What do i need to do. THanks for the help