PS3 sound questions, advice needed

i have a ps3 hooked up to a marantz sr7001, and I was wondering if I can get my ps3 games to play in 7.1 surround sound. The other day i was playing Mgs4 and was not hearing anything out of my back speakers.


Also what setting should I put my reciever on if I want to matrix 5.1 sound to 7.1. "in case the game im playing only supports 5.1" Also if they matrix the 5.1 to 7.1 would'nt that technically be 6.1.


also in audio what sound settings should be checked in order for me to hear 7.1.


last when watching BD movies should i just leave my ps3 on LPCM and leave my reciever on auto detect. And if thats correct what do I do when i put in regular dvd's if I want to hear sound out the back speakers.