Ichoose to separate the grounds but some installers choose to run them to the same point. If you choose to run your ground wires to one point you can also use a distribution block. If you do not use a distribution block then you will want to stack you ground wires so that the largest current carrying wire (usually from your largest amplifier) is on the bottom (closest to the ground point) and that your smallest current carrying wire is on the top (closest to the head of your grounding screw).