I agree you must need the XU4 when you have a 5~6TB HDD filled with a million MP3 files. The scanning & DB generating time would be much faster thanks to the USB3.0 ports and much faster Octa-core processor. But the fan might be noisy.
It looks like a conspiracy. At the forum hardkernel also manufacturers are silent on the support of the I2S protocol for the DAC. This will clearly undermine the sales of their younger computer models on which they earn the most money, as well as on accessories.