Upgrading the sony system (not TO the sony system)

[kindly9]

Hi, as my speaker system sounds beat to hell by now, I'm looking to upgrade the 8 speaker setup (well ford counts each of my rear coaxials as two Speakers for some reason).

I came upon the focal drop in kits located here: https://www.focal-inside.com/ford/en/ford-fiesta-vii-2011-2016-2-2/ but each of them are marked: "The system is not compatible if the vehicle is already fitted with the factory premium Hi-Fi option."

What gives, I know that the speaker dimensions are the same 6,5 inches, the spaces for the magnets should be identical (or bigger).

[Aldridge Andy]

If you had the Sony system back in the day I’m sure the Speakers were supposedly upgraded too. I’d be very surprised if the fitment was any different between standard and hi-fi.