Dreaded wall unit

In order to purchase my stereo equipment I had to make an agreement with my wife. Stereo stuff is find as long as it can not be seen. I had a really nice wall unit made to order using my equipment dimensions to dictate design. Here is my quandry. The speaker monitors are inside an enclosure. The speaker mesh covers are removed and the face of the speakers are 1 inch behind custom speaker mesh plates that are attached to the face of the cabnet. Would lining the speaker enclosure with sound absorbing material make any difference in sound quality? If so what would I use? I was looking at Dynamat but it is designed for cars,is quite expensive,and looks lke aluminum foil. Any suggestions aside from removing the wall unit would be appreciated