Grounding is important anywhere there is electronics, as that can be one of the (many) noise sources in a piece of equipment. In an ideal world, every piece of electronics in a box(car, boat, home stereo)should have their power lead and ground lead come directly from the power source, without anything else attached to it. (Technical mumbo jumbo) Ground noise occurs when there are multiple currents flowing through the return wire back to the power source. Since each current is not static (i.e pure DC) because the load demand changes over time, you can get what's called Ground Bouncing where the voltage measured from the power source ground to the ground terminal on your electronic piece is never 0 volts (bounces around). This noise can show up in amplifier outputs as a buzz, or at it's very worst, can reset/hang up your electronics. (/Technical mumbo-jumbo)
Always Always Always run stereo amps, stereo's, cd changer grounds back directly to the -ve post of the battery. This is where the source of power comes from--->this is where it needs to return. No roundabout paths (i.e attach to the block or something silly like that)
And for god's sake, fuse your + line right at the battery!!! (just incase you haven't done that)
Trash
P.S Jeremy... Just making sure is all