ok, then it is most likely your “video output card”.
i am on a mac system, so perhaps this isn’t true for windows, but neither your processor
nor the gtx680 should be your bottleneck. i have the extreme3d built in and never had
a problem with realtime monitoring.
i do know the usb3 problem from my sharkoon dock, there are also some compatibility
issues because of its built-in usb3-controller-chip, and therefore it connects only as
usb2.
you could try to monitor in 8bit and see if it gets realtime then, but in the long run i would
go for a proper blackmagic-video-card. bm recommends the extreme3d but i’ve heard that
all the decklink-cards are using the same driver and therefore theoretically it should work,
practically bm isn’t really testing any other setup as far as i know, but perhaps someone
from bm can chime in?
4k sounds good, but then again, who is ready for 4k monitoring yet?
andy