Lots of people have been on C5x64 and Kontaktx64 since shortly after C5 was released, it’s Giga which is the oddball. Can you not ditch it, and convert your libraries to Kontakt? I’m assuming there’s a good reason not to, so you might find some more like-minded users in the VST instruments section.
I believe some users have solved this using FX Teleport.
What I can tell you is that the HDSPe range from RME are the best I’ve ever used and TotalMix is unsurpassed for flexibility. With the RayDAT you can chop and change your converters as long as they have ADAT without messing with drivers, and RME drivers are most stable you’ll find.