Got my Sat II's for my Quintet III from Digital4cheap.com. They came with the Quintet III adapter along with many other adapters for various applications.
Check one of the previous messages for install instructions, as the ones that come with the stands are of little help. Two of the round head screws supplied worked on the Quint's, but I had to use the existing swivel mount screws (smaller head) with some small washers to mount other one until I find additional screws. Hope this helps.