Yes, in even the most exotic systems you'll hear varying small amounts of hiss with your ear right up to the tweeter. Whining? No, that maybe an indication of another problem.
Plugging the system into a single power strip channels the systems ground into the power strips ground wire. Plug the power strip into your wall receptacle and listen for any change. Then, use a three prong into two prong adapter "cheater plug" at the end of the power strips plug. Plug that into the wall receptacle and listen for any change.
Physically checking all the wall receptacles within the circuit in question will be done with that circuit disabled at the breaker box. A receptacle could still pass current even with a loose connection, this is what happened to me. The loose connection created resistance and eventually caused intermittent noise and interruption. Yes, the receptacles need to be pulled out just far enough to check their connections. Over time and hot and cold the connection screws may need tightening. If your not experienced with working with AC wiring call in some favors or hire a professional.
After I repaired my loose receptacle I decided to have both the two channel and HT circuits completely rewired with more robust metal clad cable and 20 amp dedicated breakers. Total cost by a licensed electrician was $375. in 2001.