An HLCD speaker will reproduce without a filter any noise that is delivered to it. But speakers do not 'hiss'.
All signal processors, and especially an EQ, will create some small degree of hiss. Some more than others. The hiss is usually only audible when the sound level is low and the engine is off, so under more quiet circumstances. Usually it becomes tolerable with the right system set-up technique.
You have a 4 volt source unit followed by an EQ with even more line voltage. So the gain is through the roof. You should have the amplifier input gains way down with this combination. Remember that when the amplifier gains are reduced and set correctly, this will not reduce the amount of power the amplifiers will deliver...even though your perception may have you thinking otherwise.