I have an 07 ST, I installed an AVIC D3 and I have had JL audio XR570-CXi as well as a JL audio a6450 6 channel amp as well as a RF 10" sub, I love the sound of JL audio speakers.
I probably had those Door panels off 15 times over a 6 month period, they come off easy, 2 screws behind the handle, and 2 or 3 screws along the bottom, then pull strait up an inch or so.
Putting them back on, just line up the clips, and just drop it down lightliy, then tap in the top and replace the screws.
I would recommend some sound deadening while you have them out, the plastic vibrates a bit. good luck.