A:Answer Plugging in two units is fine. It’s what you connect to those units and any other appliances on the circuit that make a difference. I would not.
If it is a dedicated circuit, 20 amp circuit, then yes. You should be fine. For instance, a sub and amp along with other normal lower voltage appliances like Xbox, cable tv box. Will be fine on dedicated circuit because they will not all be on at the same time.
Treat it like a surge protector. Too many appliances and you’ll get the flickering light, vacuum cleaner effect.
I am not an electrician or engineer. I have doec’d a few home theaters as my reference. Stay safe