Help required - Optoma HD66 set up to Sony E280

[jodi]

I just got optoma hd66 and I connected to a dvd player and they both are on the entertainment center and it works fine, however sound is not loud enough to watch movies. I would like to hookup my sony 5.1 e280 system to the projector. Please help. Does the projector has to be ceiling mounted? anybody tried on a table/entertaiment center, if so can you share information. Thanks in advance.