Jarre...
What car do you have mate? Would it be easy enough to take the standard ones out and put these in if it wasn't dark?
I have a 2010 Leon mk2. Yeah its easy enough to do. The sak 3103 comes with the speaker adaptors, they're plug and play, simple. And it also comes with a plastic adaptor, which basically acts as a buffer to push the speaker outwards to where your standard one will be (so theres a bigger rear box so you get more ooomph).
To install: Take off the speaker grill, undo the 4 torx screws, remove speaker and unclip the adaptor. Then you can install the plastic buffer, this just screws into place (you can use the torx screws you just took out). Then plug in the speaker cable adaptor, attach to the speaker, then put the speaker up to the plastic adaptor, screw in 4 screws, replace speaker grill. done!
I tested them before i screwed it in just to make sure it was okay... didn't want to remove loads of screws if something wasn't working! Had it not been raining i'd have been done in 45 mins easy, took me an hour and a half as i was sat in the car, leaning into the footwell, not seeing what i was doing, getting stressed as my torx screw driver wasn't quite long enough so i couldn't do 360 degree turns, just 45! you get the idea haha...