kicker system in 06rsx s

Hey guys, I am installing a new kicker system consisting of a zx700.5 amp to power ks62 components up fron and ks62 coaxials in the back as well as one of the premade loaded sub enclosures by kicker. I will be grounding the amp to a known good chassis ground bolt behind the rear seat. I am not anticipating alternator noise. My question is this, When I wire up the headunit should I just use the pre made metra harness or should I run a dedicated power wire to the batttery for the headunit along with the amp power wire which I will be running anyways so getting another wire in there wont be a big deal. I think running a dedicated 12 or 14 gauge wire to the bat should be better fro preventing noise than taking it from the harness. What about grounding, should I use the factory ground wire in the harness or should i ground to a bolt behind there which has low resistance to ground. Thanks in advance

Any ideas?

First thing I would say is make your own ground while its true that an existing bolt can be a good ground on occasion you should always bolt/screw/attach directly to the bare metal of the chassis. Generally bolts that exist are put on directly over paint and are not the best points of ground as for your second question I normally run power directly from the harness and have no problems however there are some headunits out there that are very power hungry (older alpines with the separate power brick come to mind) So depending on the headunit in most cases though power from the harness is fine.

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2008 Scion xB
Pioneer AVIC-D3
RF 3Sixty.2 sound processor
Stock speakers (for now ;))