I will be installing a un65js9500, and I understand that it has the larger 14"+ box. Now, the below will not work for me, but you may want to consider the below box (or contact the manufacturer to see how if would work with the mount for your TV.
You may be able to install this as a recessed box between two studs behind a two-stud wall mount, and it should hold the box. If I would use that size box, it looks like the larger one connect box would have to jut out somehow, and i would instead need to use a larger leviton box,
on amazon leviton-47605-21E-21-Inch-Structured-Enclosure
which will not look good once the TV is pulled out from the wall.
Also, I just chatted with tech support and apparently the 10 foot cable for the mini box is not compatible with the larger box, or it would work for what I need to do, which is route it over this mount
which extends two-feet, inside the wall down at least two feet, and then into the entertainment cabinet. I could maybe do it with the 6 foot included cable if I have the one connect on the wall behind my entertainment cabinet, but I would rather have it mounted inside.