Rear speakers need to have the panels reinstalled if you want to hear what they sound like properly.

The A/B test of Pyramid 4 X10 vs Alpine 6 X 9 is not valid unless you reinstalled the panels.

For a speaker to have any low frequency response, the font of the speaker must be isolated from the rear of the speaker. The entire concept of how the speaker works is by small changes in air pressure. If the front and back are in the same "air space" then it will sound like crap, no matter the size or quality of the speaker.

In the DMC, the cover panel is what controls the air between the front and back of the speaker. For better sound, add some weather strip foam around the speaker to get a better seal against the panel.