Help with connecting PS3, Surround Sound, and LED-TV

Hi everyone, this may be a stupid question but I can't seem to figure out the answer. I plan on purchasing a Samsung 55" LED(dumb, not smart) and a PS3 soon. I currently have about a 4 year old Samsung theater system http://www.samsung.com/us/support/owners/product/HT-Z310 is the page for the model. The problem I forsee running into is that the TV only has 2 HDMI inputs. I will be connecting a Comcast HD cable box through one HDMI input and the PS3 for the other. I was wondering if there is a way to connect the PS3 through the Samsung unit and somehow have it pass the sound from any blu-ray 5.1 movies to the surround sound system while still playing the hi-def picture? Is my only option to unplug the cable box each time I want to watch blu ray or play PS3?

Connections on the back of the A/V unit are HDMI out...Optical IN...component out, and video/audio out.

I hope that my explanation made sense!