Hi,
I installed the last Bios from ASUS on my my Asus-Z87-Plus with Intel Core i7-4770 Processor. (uninstalled all Graphic Drivers then installed the latest one (feb. 27) after having installed the latest Bios Version from ASUS.
I still have the same sound problem. (The sound works good if I connect only my52 inch Sharp Aquos TV through a Yamaha Amp. HDMI in and out. But when I connect my Monitor on the DVI output, the sound turns off. It comes back on if I diconnect the DVI output.)
Hope you will find a solution soon. This Graphic Chip is present on a lot of quality motherboards, and buyers are waiting like me...