They are good and do really improve the sound but only to the same level as dynamatting but the benefit of dynamat over these is they dont stop reverberation into the panels where as dnyamatting holds the surrounding area tightly with the sticky rear of the mat not just the area around the cone.
personally i would stick with dynamat as you still have to cut a hole in the back of them to pass the wire through effectively youd loose any benefit from having an enclosed rear