On the main (arrange page) .. click with the right, now choose add group channel... name it according 2 what u need , press f3, now u have the mixer, under each channel u want 2 route press on the out tab (generally buss 1 our master) and now u also have the option 2 send to the newly created group!!



...

2 send outs 2 yer sound card... go to devices, choose vst outs, activate waht u need... do the same as above... mind u I haven't tryed this with sx, but seems logic that it works this way!!

Hope this helps...