This is what I meant about the stock rings, but you answered it. http://www.focusfanatics.com/forum/showthread.php?t=276050
I also guessing that when you said 2x $2.99 that means you need an adapter for all 4 doors?
DO you have any pictures of where you put the amp? You said in the hatch floor, so did you take your spare tire out or cut a section out of the styrofoam subfloor?