Depends on connections, I have similar setup as follows.
HDMI connection from TV to PS3.
Optical connection from tv to Home Theater. The sound via HDMI to the TV is 5.1 (Which I am assuming your tv supports since it has an HDMI connection) The optical connector to Home Theatre System is passthrough sound from the tv. When I want to here the Home Theater, I just switch it on and mute the TV for 5.1 surround sound. Sometimes I can't be bothered and I still have sound through tv too. I also have a DVR Satellite dish connected via HDMI to the tv, and it lso works the same using the Home Theater whenever I want 5.1