Air circulation is key. I keep my 861v2 on a shelf in the closet with other equipment. If the weather is warm / house is warm and I keep the door to the closet closed the unit will get quite warm / hot even in standby. If I crack the door open and allow for some airflow the unit does not get warm at all. The closet holds an amplifier, DVR, and PS4 all of which generate some heat.

558.2 amp, Meridian A500 speakers, M2500 sub, Director & Explorer DACs