The boxes will have to be removed prior to installation, but you should have at least 16" off empty space. If you dont have a stud finder, you can use a metal coat hanger. straighten out the coat hanger so that you have an "U" shape with about 12" on one side (the other can be shorter. poke the hanger through the sheet rock right next to the box. insert the long end and spin. you will feel if it hits a stud or other obstruction. this will allow you to gauge how much empty space is in there.
my first thought is that if someone put a box there, you should be able to put a speaker there. worst case scenario "wall mount"
I got the pistol so I get the pesos