Do i need a capacitor?

87 s10 alpine HU with built in 50 watt 4 chanel amp powering my dash 4x6's and the door speakers. The subs are two cvt12's (800 watt peak each) with a 750 watt kicker amp in other words the system is only about 800 watts. i was gonna get the optima yellow top and the alternator is high output with all of the wiring done heavy. i heard u needed one for over 1000watts rms but wasnt sure