Okay I have to use two hdmi outputs from my graphics cards (GTX Titan X) to my TV (video) and receiver (audio). 
 
Reason is, my TV supports 4:4:4 chroma @ 4k @ 60hz, while the receiver doesn't support anything above 4:2:0 at 4k @ 60hz. So, I have to bypass the receiver for picture but need it for sound. 
 
Using the second output (DVI>HDMI) or even using the hdmi on my secondary card (GTX 780), the problem is, in order to pass audio, I need the second output to be enabled as a display. 
 
This means extended desktop mode. I can't use duplicate mode for some reason because it brings the resolution down to 1080p. 
 
Because of this I cannot use windows snap (which I use a lot) and sometimes my applications open on the other "display" which happens to be my receiver. 
 
Is there anyway to make it that my secondary output ONLY outputs audio and no video? I may try modifying the edid of my receiver for 4k @ 60hz to see if that allows me to at least do duplicate mode but any other suggestions?
 
Thanks 

I've been trying to modify the edid with cru to no luck. I get one asterisk next to the display. 
 
Hopefully someone knows of a solution, the mouse going to the other display when in the corner is also very annoying. 

I had to resort to using the MB optical (toslink) out to the receiver.  Windows ability to ID digital receivers is sorely lacking, so many glitches.