do I need a capasiter for my system I'm installing? 2 MB Quarts', 2 ALPINE 6x9 SPS-690 3WAY, SPS-170A coaxial for the doors, and a Alpine DVA- 9860 head unit. I'm running the 6X9 with a Alpine MRP-T220 50rms @4 and the subs are beening puched by a KICKER 800.2 for now.

 

Caps are worthless man.
Spend your money on a new battery and/or big 3 upgrade.