according to the manual supplied with your ps3.. rca outputs (red & white cables) can produce 2.1 surround maximum.. for 5.1 u have to use optical (the optical out port behind your ps3) or hdmi output (which supports 7.1 surround max)

as for myself i use an lcd monitor.. with video coming from hdmi.. and 5.1 audio from optical output on my logitech z5500..