Guys, I have the same problem: I have the NUC DC3217IYE.
I select one of the 5.1 Surround options and play the Test sounds. I hear audio in the front left and front right speakers only and nothing when the center channel, subwoofer, and both rear speaker test sounds play. An even more interesting fact is that when I try to "Test" the device from the Playback device list, I hear the same two speakers, but when the other speakers are supposed to be playing sounds, the audio level indicators actually jumps up but of course no sounds is being played.
I noticed the same behavior on my Laptop - also with Intel HD 4000 graphics - it seems a real driver error? I have the latest Inter driver bundle for NUC from November 2013 and all Windows 7 64 Bit Updates - no change. The problem exists always when you I try play sounds with 24Bit.With 16 Bit it works.
When will it be fixed?