To further explain, to display a 4k one needs a 4K panel. If one does not have a 4K panel, one needs to down rez the source into the number of pixels the panel can display. Fine and dandy. The JVCs use 1080p panels. They can display a 1080p source. Anything higher, and they can't display it. At present there aren't really any 4K sources available to consumers anyway. Why have your Oppo upscale 1080p to 4HD when even if the JVC could accept it, it would just have to undo what the oppo upscaled? The Oppo could upscale and feed the Sony but then the question would be, which upscaler was better, the one in the Oppo or the one in the Sony.
so what's with the JVC displaying 4K. By shifting every other image frame over and down one half pixel and by scaling 1080p sources to 4k internally and then by massive processing extracting two very adjusted 1080p frames so that when flashed, with a pixel size that overlaps the pixels partially, one gets 4Hd pixels on the screen. really only 1080p at a time buy flashed fast enough so you and your eyes are tricked into seing 4HD pixels. rather nifty but not the same as having a true 4K source and displaying it as it was shot with one to one pixel mapping.