Kenwood KAC-8020 Service Manual page 13

Since the power amplifier has no parts which require operation, it
can be installed at a position away from the driver's seat without
any hinderances. But due to its considerable weight, it needs to be
installed securely.
As generally accepted positions for its installation, places such as
under the front seat or inside the trunk, etc. can be considered.
Install the unit in a well-ventilated place and do not place any
(heavy) object on it.