The analog cables would make it less likely for you to get 5.1 output from a stereo source, as most receivers when using their 5.1 input only offer a "pure, direct" signal path.

As Micah said, pick the HDMI input, and look for a surround mode selection, or something similar which will enable Dolby ProLogic, DTS Neo, or something similar.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris