Rear speaker swap
Ok - start by using my guide on installing Gen 7 seats to help you remove the rear seats - this will make the job so much easier.
Firstly, please note that the stock speaker is 6" (16cm) exactly. There are very few 6" speakers still available - the Pioneer TSE1675 is a perfect fit for the standard speaker pod mounting. You could try and fit a 6.5" (17cm) speaker but you wlll need to cut more of the stock speaker mounting away.
Once you have the seat backs and seat base out you're ready to continue.
Remove the side seat hinge from the panel - remove the 2 large gold bolts.
Looking at the plastic speaker mesh, using a flat bladed screwdriver, pop the mesh off.
Remove this gold bolt from the panel.
Now remove these 2 screws holding the panel onto the seat base and back seat upright.
Work your fingers around the plastic and you can pull it away from the body.
Hint - have your door open and slide the panel towards the front of the car as you pull it away. It clips back in later - have patience !
You'll notice 2 bolts holding the grey/brown mounting pod to the body shell by the speaker cone, there's also a 3rd one at the seat base:
Remove the speaker pod from the car - there's a clip connector low down which connects the speaker wires up to the in car wiring.
Take the pods out and and mount your new speakers into the pods. Remember the paper ring as well !
Install the pods back in - not forgetting to re-connect your speaker connection (I did this - but just about managed to clip them back together without having to take the panel out again.
Then replace the plastic mesh.