When my house was built, they pre-wired the walls for 5.1 setup. Unfortunately, the didn't mark where the rear surrounds are. I don't really need the fronts because I"ll run them right from the receiver, but I definitely need the rears. I will probably call them, but I'm afraid the company is going to want to charge me to locate them. Can I find them myself? How? I've gone up in the attic and you can't see where the run down in the wall from there.