The specs at the end of the Headfonics review say the connector on the X5III is USB 2.0. Yeah, get a $10 USB 3.0 card-reader.
One of the features I really like about Fiio's (X7) "Pure Music" side, is that you can disable media scanning upon startup, which is useful if you know you don't need it, and you have a lot of files on the card you've specified as your library source. It (by necessity) also provides a manual-rescan feature if you go the card-reader route to load up. I just blow away the existing music library and manual rescan. It's quick for me, but I don't have a maxed-out-capacity card, or thousands of songs. The scanning speed, if you browse the FIIO boards, was one of those YMMV situations. Under stress-test conditions (thousands of titles, untested 200GB SanDisk cards), people got wonky results.