I leave my subs on all the time and never hear any noise/thump when turning off my equipment. Now, when I unplug my preouts from my receiver when everything is powered on, I sometimes hear a thump from my 80's that are hooked up to my Odyssey amps.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85