This is a pretty good deal. Rodney is a good seller. I bought the Sony version of this (sub and amp) and I've been happy with it. It does NOT slide around. You can't lay the rear seat down, but you can pull it down far enough to get to the jack compartment easily.
jettman, just about any speaker box you get that will fit under the rear seats, won't let the seat fold "flat". The hardware under the seat moves forward and down, so it will hit the top of the box. If you don't fold the seats very much, you can use the box and not worry about it. If you like to have the seats folded flat, then you will have to find a smaller box.