Planning to rewire my setup

hi, my current setup is as such (I think) but the wires are all going through the centre of the interior (mines a RWD car). There's a whining issue that I'm facing currently. I plan to rewire everything esp the power. I bought some 8 gauge cables for grounding. Please help to advise - where shall I ground the amps? Can I employ a star network grounding for the 2 amps onto a bolt on the chassis? - should I ground the HU to the same ground as the amp? (they are quite far apart, the amps are in the boot, the HU, in the stock position. - any other advice for questions I overlooked.... Thanks! Hope to hear your advice and criticism...!

Separate the power wire from the RCA cables.  One should be on one side of the car, the other can be down the center or down the other side.  Do that first and see if the whining problem is solved.  Then, make sure the ground wiring is the same gauge as the main power wire.  Star ground to a bolt  that you put in, not a factory bolt.  Remove paint from the chassis surface.  If whining still persists, post back.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.