Man, first time trying kick-boxing, insane work-out. Luckily I've been working out properly so my muscles weren't sore, just my cardio is very bad and needs some work. So I decided to take it easy last night and work on my audio system.
All 12 V DC relays. The lone relay beside the cap takes the remote signal from my head unit and then provides power from the battery to the other relays. This is because my head-unit's remote line is only rated for 250 mA and each coil needs 100 mA. On the top left of the first picture, you see two LED's, these are on depending on the relay's state. The left-most LED is on when the relay is energized, the right LED is on then the relay is off and there as 12 V going to the relay.
There's an LED on the bottom of the capacitor that comes on when the 4-bottom relays get energized. The 4 bottom relays are normally de-energized and pass through the speaker outputs to the internal speakers. When I flip a switch, the energize, that LED on the capacitor comes on, and speaker outputs are passed through to my external speaker connections instead.