Hi. NiVision99
Great you are getting the SM I have one and I would not part with it for $10000000 buk`s for SQ & QS its the best and don`t for get it does the best Stereo Synth to Surround to.
The 4 channel out is for your matrix decode & when you take the front 4 channel out to the front 5.1 out and connect the centre & sub this will decode DTS 5.1 & DOLBY 5.1 Surround..
Bill..
The SM does NOT decode DTS and Dolby 5.1 surround! To do so would require digital inputs.
What it can do is "decode" Dolby and DTS 2.0 outputs into synthesized surround.