OMG...... how long have you got?
just changed mine. full back seat out job.
start in the boot. undo speaker cables. bit fiddly but necessary
remove bottom seat first. then back rest. then panel. after that it is quite straight forward. took me & 1 mate about 2hrs.
will check which ones i bought tommoz for you. even though i measured the hole i had to take back the first set i bought.
the holes for the screws are an uneven off-set so only a couple of makes will fit, unless you start chopping the rear parcel shelf.
even then i doubt you will get all four screws in!
i settled for 3 in each and that involved creating a new screw hole in the speaker surround itself.
A straight bolt in option is the Kenwood KFC-1690IE 6.5 inch speaker.
It comes with an adaptor plate to fit the standard speaker mounts.
Once installed it still looks stock and you can keep the standard speaker covers.
Sound good also!
Managed to fit 6x9s in mine, although requires some work to the shelf & inserting MDF templates between the shelf and speakers helped!
Be prepared for some neck ache if you want to go down this route as theres not much room to manoeuvre due to the rear screen..