I think what he is saying is figure out where all your amps are going. Measure the distance from each amp to the common ground position you choose, then cut all the ground wires you need to the length of the longest one you measured.

The longest ground you run will be your weak link.

 

^
Ah, that seems perfectly logical. Thanks for clearing it up.

 

The important thing is to keep the ground potential as equal as possible for as many pieces of your system as possible. Actually measure the resistance from your potential grounding points to the battery and try to keep them all as similar in value as possible.

There is nothing inherently wrong with having a long ground lead as long as it is of sufficient size to handle the current and minimize resistance.