Is it possible to set up my computer and ps3 to surround sound and to a projector all at once?

It looks like the projector has the right connections for both the computer and the PS3. The problem will be hooking up both systems audio into your surround-out. The simplest solution will probably to find a switch that you plug in the audio to in say a channel a/channel b setup then plug that into your surround sound and just pick using the switch whether you are using your computer or PS3. The video should be easy though. I'm actually currently doing that on my system.