if u dont do it urself, go to a proper pro
ie. not JB , strathfield or autobarn
i had my first amp install done by strathfield, i gave them good wires etc. they used shitty wires cos they couldnt fit it and i only knew what happend 1 year later cos i had no idea about car audio then. (they used 4GA from the battery like i gave them, then as soon as they got under the carpets, used 16GA to the amp, yes 16GA..not 8GA, no dist block or anything)
i ended up ripping everything out, doing it properly, which u will too later down the track im 99% sure