OK, so what do we know so far? Snapdragon 660 SoC, 6GB RAM, 64GB ROM, most likely very fast performance. Then, volume wheel which reminds of DX160 and has a power button inside, very convenient to turn the display on/off while keeping your thumb on the wheel.
And, the next clue is modular design. Most likely amplifier module (not dac/amp), bigger in size and also slimmer since chassis look quite slim. Obviously, module is associated with headphone and/or LO jacks so theoretically it should slide-in from the bottom. We got the first shot of DX300 bottom, and it was intentionally left blurry. I just cropped that part and zoomed in, still very blurry. But, is this my imagination or could there be 2 screws closer to the edges, if you look from a distance? Also, something is between 3.5mm and 4.4mm ports?