I made such a system for a friend of mine who has muscular dystrophy. He is a music teacher and almost totally paralyzed. He has a van he drives with joy sticks!
I used Corian and MDF for the plates and Focal drivers. They do not sell individual drivers any more. The subs were 12" Dayton Titanic 3's in Corian enclosures. We used a TACT preamp and amp for the plates and a QSC amp on the sub woofers. The Tact provided the cross over. The plates hang from the ceiling with the subs below. I still get compliments on that system. The goal was to give him the best possible system for as little as possible and we beat the $8000 limit.