I assume you have an older home with thick plaster walls over lathe. This means your walls are very thick, which renders your studfinder useless. In that case, drill holes and use molly bolts. This will hold a lot of weight. Another technique (similar to the Dogeatpuppy response) is to find one stud by drilling small holes at regular intervals of about an 1/2 inch apart 16 inches from the corner, and then measure from where you hit a stud.
The wall has to have studs or I would be moving asap as you have some serious issues with the integrity of your walls.
However, if I understand your situation, my advice would be to move the stack of components to another wall and use longer cables to whatever needs to be on the TV wall.
