The connectors and wires are in fact there, but your audio amp up front won't have the proper outputs. You will need more than just speakers....
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You have to remove the entire inside plastic trim piece that contains the speaker grilles. To remove this you need to remove the top plastic bar (top of liftgate window) and the left and right side pieces (...lots of blue clips). The large bottom piece is held by a lot of clips plus 2 Torx screws. You have to unsnap the recessed plastic hand holds on the lift gate and also pop out the power liftgate button first. And when you start to drop this large trim piece, watch out for some short wires. And if you enjoyed this, just wait until you try to reinstall this large unwieldy piece--it's a 2 person job for sure. YMMV.