While those plugs adapters do lift the ground, that's not their intended purpose, which is to alalow a 3 prong plug to be grounded when the outlet only has two slots. The green tab or wire is supposed to be screwed to the junction box via the screw that holds the wall plate in place.
That being said, be careful in how many pieces of equipment are touched while using this adapter- if the chassis of something becomes electrically 'hot' and you touch something that's grounded, YOU become the load and that can be lethal.
To test this system-
Connect the power cords as intended before starting, without any cheater plugs.
Disconnect the XLR cables between the Anthem and the amps. Listen for hum- if it's gone, turn off the power to one amp, reconnect the cable and turn it on- if the hum is still gone, do the same with the next amp. If the him is still gone, connect another amp. If the hum returns, disconnect one of the previously connected amps and try again. If it stops after either previous amp is disconnected when everything is connected to the same outlet, through nothing but some kind of unfiltered power strip, you may have slight resistance on the neutral and/or ground connection. Ground loops are caused by voltage differences (called difference in potential or potential difference- electricity is Potential Energy),which causes the electricity to make up the difference wherever it can- if it happens to be on the audio cables, it really doesn't care- it wants its connection.
Your amplifiers and AVM60 all have a ground screw on the rear panel for a reason- use them.