I'm probably making things complicated...

What is a proper ground?

A poor ground connection or high resistance reading may seem trivial under no load, but once you are pounding your nice new amp and it is drawing large amounts of current, this little reading has become a monster reading that has caused many an amp to fail for no apparent reason. It may be noticeable as a extremely hot running amplifier in a short time period, poor output levels or diminishing levels and of course a blown power supply or output section in the amplifier.
If we had CSI go back and look at majority of amp failures...this is it.