if your MX -136 does not have multi channel RCA input, then you need to use the MX-136 HDMI input from the Oppo in order to get surround sound.
The Oppo's 2 RCA outs are for the audiophile stereo only section of the Oppo and will not get you multi channel sound.
The Oppo's 2 RCA outs are for the audiophile stereo only section of the Oppo and will not get you multi channel sound.