I put wall plates at the amp and speaker locations for one reason: WAF. She insisted, and I cried afoul of all of the possible EFI this would introduce. I thought I was going to be Mr. Smarty and give her the ol' A/B comparison to show her how she ruined my audio world.

To my surprise, there was no audible change.

Now I'm glad I did it, because people buying houses typically don't like to see wires hanging out of walls.