As surroundophile points out, the 950 lacks an HDMI input, and thus cannot accept a multichannel PCM signal (optical and coaxial can't carry more than two channels of PCM). The standard alternative for folks with HD-DVD and Blu-ray players who want access to the new audio formats is to have the player decode internally to multichannel PCM (for DD+ and TrueHD - BD's with PCM tracks don't need any decoding) and output multichannel analog to a 5.1 input in the receiver or processor. The PS3 does not have a multichannel analog output, however, so you are limited to the optical output. For discs with multichannel PCM tracks, I believe that the PS3 will downmix to PCM stereo, at which point you'll be relying on Pro Logic II to achieve surround. If you use the Dolby Digital, DD+, TrueHD, or (if you encounter one) DTS-HD tracks, the PS3 should send the core DD or DTS track out via optical to the 950.
If you have turned the center off in the 950's speaker setup, then the 950 will properly generate a phantom center by mixing center data into the front speakers.