Well, finally got the ARC. I don't have my HD6xx's from massdrop yet, but i'm using my SennheiserHD 25's in the meantime, and yup, sounds better than my supposedly decent Realtek ALC1220 onboard sound. No static noise, clean, flat, loud. Not the best heaphone's to test it out with, but a noted improvement. Mic input seems decent too, but haven't tested it out too much yet.
PS4 via USB - it just worked, and much, much better than plugging the headphones into the Dualshock, I can't express the difference. I knew the dualshock output wasn't good, so I shouldn't be surprised, but it's pleasing that this all worked so easily, mic seems to be detected too, but I haven't been on voice chat yet with it. I hear PS4 can be problematic with USB audio devices, so I'll keep an eye on this long term for issues.
I think i'll get a USB type-B switcher so I don't have to uplug/re-plug when swapping from PS4 to PC. I don't want to deal with optical and pass through mic crap, USB or nothing! Hope I can make it work.
One thing I noticed, and this could be my windows setup, PS4 via USB is much, much louder than windows via USB. On PS4 I had it on notch 1 or 2 and had to turn the device volume down in dashboard settings. On windows I have the ARC cranked midway, and windows voume between 50% and 80% (have a slider on my keyboard). Don't get me wrong, both are perfect sounding, just noting the volume disparity. Could be my windows, or the realtek crap that's still floating around my system.
Can't complain though, it's just so clean and nice of both devices. In fact I'm probably listening at dangerously loud settings because it just sounds so full and distortion free at high volumes.
Very happy I bought this so far.