To know if you can connect your equipment to this circuit then you first need to add up the load of all of the devices that you will connect to it. Open the breaker for this circuit and identify all receptacles and lighting on it. If it is a 15 amp circuit then you are limited to 1800 watts max. If it is a 20 amp circuit then you are limited to 2400 watts max.
Add up the total load of all the tv's devices and if you fall under the above limits then you can tap this circuit and install another receptacle. You do not need to cut the cable to do this. You just need to add a piece of Romex wire of the same gauge between the existing receptacle box and the new receptacle box.
This link will show you how to do that and how to connect the wires.
http://www.rd.com/content/openConten...ontentId=18145