first thing install the damn HID's this will make a big difference and you have already spent the money to buy them . You will reduce your dimming, Next do the big three since it is cheap your cost is wires no more than $50 bucks and that is pushing it. Call optima and talk to them when i use to sell optima and what i was told use yellow top as a backup battery beside your system for reserves as it is meant to be drained all the way and then recharged. If i am not mistaked red top has higher CCA as you will be using it as a main battery to start your car. Cap is not neccessary right away since HID, Big three and a battery should make a significant change. Last add the cap to stiffen the sound system and your power issues. You should be running your system right off the battery direct to get the most amount of voltage and no regulation as your amp will regulate the power. So when you do the big three tap the amp off the battery. Buy some good battery terminals. I use monster terminals as the have some good posts and can easily wire in other aux output.