Hi

First I guess you unplugged the EMPEG at the amps to prove the amps were the source of the noise.

The second thing is: Are the speakers' negative terminals grounded at the doors as this will lead to problems and if so use the negative connection at the amp.

The third thing is to look at the amplifier main supply ground (while the EMPEG is unplugged) as the quality of that is as important as the positive supply. You are hoping the noise will go away with a high quality ground connection.

Lastly and most likely, If your amp is running bridged into two channels then common mode voltage between the amp channels can cause noise. Select 4CH mode and if the noise dissapears then great. Sort of great, as there is design fault in the amp so choose another.
Experiments with common mode voltage
1)shorting the amp inputs together negative to positive - should remove the noise
2)shorting the centre input to the EMPEG ground - will make some small amount of noise

(Common Mode voltage: parasitic voltage between the two bridging amplifier inputs. It will create an unwanted audible signal even with no input in bridged mode, but not in 4CH mode. The sound may change up and down with the battery voltage or may be static.)

Cheers