ok since you dont want to trade ill let you in on why you get ground noise in the pioneer h/u.
just to let you know i have the avh 5700 also.
open the radio up, yes open it up. you will see a little fuse there on the board near the rca outputs, that fuse is the cause of your problems, it is blown, take it out and replace it, this is the connection between the radio ground and the rca ground and thats where you get a ground loop from, as you have stated alt whine.
this is the correct way to do it.