I used to wire homes in the early 80s to feed and clothe myself. I learned from Mr. Nakamura - a top notch high school teacher and master electrician who also taught me how to treat girls. The ground wires from the lumex/romex cables are marretted with pig tails terminating at the junction box and receptacle grounds. Don't rely on the receptacle mounting hardware for grounding.

Mr. Nakamura passed away but I still practice his techniques to show my respect.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated