I agree with everything Scoobywagon has said but I have a tid-bit to add. If you do run all the wires down one side you should get two faraid nodes. Faraid nodes are, in most cases, round magnets that you should loop the RCA cable through near both ends. Loop the RCA cable through a node behind the deck and once more at the first amp or RCA splitter of you are going that route.
Your computer monitor data cable uses a faraid node covered in plastic and in some cases its on either end of the cable. It is great for cleaning garbage signal out of a 12 foot RCA or any data cable.
PM if you need more info. 3 year robotic club head builder/engineer:banana:
PS. If your still getting light dimming get a capacitor. Some people don't believe they work but my 93' Impreza would beg to differ. I put it right between the battery and power distrabution/main fuse panel and it even started better!! 1 Faraid per 1,000 Watts rms not peak