Ozzy, it sounded like you were thinking about running a wire from the Entreq to the duplex ground. That would seem to defeat the Entreq as the path of least resistance would be the component to the duplex ground. So why not just try the duplex ground or ground rod w/o the Entreq to see if they are equal in reducing noise? I believe these purchased boxes are no more than representatives of our earth(dirt, etc.) and the cheapest way to replicate them is to go straight to ground. The bigger the boxes, the better the reduction, i.e. the more "dirt" they represent.🤷♂️
I'll try grounding my negative speaker terminal to earth ground rod this weekend after I change out the purple fuses first in case there is a short I am not anticipating. I have tried grounding the mounting bolts of the drivers to the earth rod with zero effect.