I have my XBOX hooked up to my Integra 7.1 receiver via the optical jack on the XBOX High Def package. When I start up a game the receiver will recognize that it is receiving a Dolby Digital signal. While playing games such as Halo and many others, I can hear the various discrete sounds move from the left front to the right front speaker. However, I do not get sounds from my rear speakers or my center channel. I get sound out of all speakers while watching cable and DVD's. Is this normal?????????