I had a look at replacing rear speakers last nite, gave that a miss and looked at the front. It is all to time consuming and at 9pm especially when you dont have any tools to make any adaptors anyway.
I have given it a miss, as I was only trying to speed things up. It's goes in the morning to Installer Services New Market to get all fitted anyway.
You can get to rear speakers, just the plastic moulding (top plate) does have to be broken from the secured platform.
I have a CQ-C9800U head unit (70W x 4)
and then have some cheap speakers to run just so that i dont blow the factory ones. Don't have any money for the real stuff yet.
Will let you know how it all goes.
Stephen.