I wired the rear speakers up today - as luck would have it, one side of one of my RCA patch cords from the stereo to the amplifier was bad. Installed a new patch cord. The rear Infinity speakers now sound great - also providing something of a massage through the seatback. Bass is much deeper with zero unwanted body vibrations coming from the factory rear corner speaker areas. I temporarily installed the FAST E6 ignition box directly below the Kenwood XR400-4 amplifier and ran the engine. There were no electrical interference surprises from any direction. So, the FAST E6 has found its home centered under the Kenwood amplifier. As for the factory speaker positions, they will become lockable, insulated, and sealed storage areas. All that is left is minor audio adjustments to the Kenwood eXcelon KDC X998 headunit using one of my favorite oldies albums - like the Raiders Collage album Mark Lindsay worked so hard at mastering with analog equipment.