If you look at the photo above you'll see the harness and ground loop isolator I'm using for a nav unit i'm going to install. The harness has four RCA jacks, front left, front right, rear left and rear right. The Ground Loop Isolator has only two inputs, left and right. Should I run the front left and right or the rear left and right through the isolator, or do I need two ground loop isolators?

Edit: Nevermind, I've realized I'll need a second one for either the rear or front speakers. I'll try it out first without the ground loop isolator and judge how it sounds.