To an input pair inside Plogue, most likely, via Soundflower (since the first two Soundflower inputs are likely to be where the Vienna Instruments player sends its output).
Except that I'm stuck in RME Fireface 400 land, having been working with it for a review. Audio Driver + Sunflower is only going to go to an audio interface output, not into Plogue, so that doesn't work. The RME box has internal mixing, so software outputs can be routed to any DAW input.
Maybe I'm not as clever as I thought I was. You still have Soundflower and Soundflower + Audio Driver; I think that would give you two different routing options with Soundflower. But that may be another hole in my thinking.
Except that I'm stuck in RME Fireface 400 land, having been working with it for a review. Audio Driver + Sunflower is only going to go to an audio interface output, not into Plogue, so that doesn't work. The RME box has internal mixing, so software outputs can be routed to any DAW input.
Maybe I'm not as clever as I thought I was. You still have Soundflower and Soundflower + Audio Driver; I think that would give you two different routing options with Soundflower. But that may be another hole in my thinking.