Audio Systems: Car speaker humming.., jeep grand cherokee, infinity speakers

Question
I just finished installing a new pioneer head unit, as well as two subs and an amplifier for those, in my 93 Jeep Grand Cherokee.  When I turn the key to accessory everything works perfect, but when I roll it forward to On, I get a hissing noise from the two front right(one in the dash, one in the door) speakers.  Any ideas as to why, the Jeep has Infinity speakers that came with it and their own amplifier.  Im stumped grounds are solid and my connections are tight.  Any help is greatly appreciated.

Answer
I think it is a compatibility problem with the Infinity speakers/amps.  You may have to add filters or replace the speakers.... I am not sure on this model.  May I refer you to Ernesto who has more experience with this type of installation problem.  He is at:

http://www.allexperts.com/ep/835-69262/Audio-Systems/Ernesto-R.htm

Good luck.