Ah, that distance, where you can tell the difference pixelwise or not sort of thing with 4k. Not the only reason to have a 4k set from what I've read (still happy with my 1080 thanks), and I sure as heck am not going to sit as close as 5 or 6 feet just so I can get max pixel advantages
Yes, sitting that close isn't good for good audio, at least not what I want out of my audio visual experience....whether that's definitive for you I don't know, but it is for me
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Where are your surrounds? Did you rerun/reset calibration of the speakers with the avr for that distance?