The Dsubs are a diversion - they are just a way of making a connection. You are still left with balanced signals at the the patchbay, and what I and others were saying earlier about balanced inputs and outputs still applies. When it comes to whether you can use TRS plugs on equipment specified as having unbalanced I/O, it depends on how it's been implemented inside the equipment's chassis, and you would have to check every piece. I've got some effects units that are unbalanced, yet they are fitted with TRS jack sockets with the ring unconnected on the input and grounded on the output, so it's OK to use TRS cables, except when being driven from floating outputs. When driven from non-floating balanced outputs, you lose 6dB, as expected.