Speaker sound baffling

[07TR]

So I recently installed the kicker audio speakers in my mustang and the one video I watched they showed using spund baffles around the speakers which makes sense but on the rear deck they also added more material and I was hoping someone could tel me just how much this changes the sound quality and just in case your wondering I'm running the stock head unit for now until I can get a digital display one that is Bluetooth capable. I just want to get a feel for it it's worth it to go back and take the car all apart again to add in that material to the rear deck and I plan to try and install my sound baffles from the bottom up this time