The amp and sub's are easy
-run a seperate power from the battery to the trunk (red)
-there is a blue line line from the HU (the remain) run that to the trunk
-the ground (black) drill a hole in the trunk (make sure the gas tank is not below), and screw the wire there.
After that, piece of cake, connect red to red/blue to blue/black to black on the amp. Run the wires to your sub.
Note: 1 12" sub is good enuff, as long as its in a bandpass box.
I used to have Orion XTR, but i fried it, JL audio or Kickers are Fierce !, oh, spend the xtra $$$ on the HU, I dunno what ur budget is but you can get one with a built in LCD as well.

Good Luck