Do not buy an Astell & Kern 120.  It claims 192Gb memory, but it indexes and uses only the internal memory - 64gb. The external SD cards carry files but do not show up on the device.   Money spent on the two mini SD cards is totally wasted - the files for all intents and purposes do not exist.  The software index the tracks alphabetically so you must listen to your music in random order.  When using iRiver Plus4 the software does NOT rollover automatically from one memory unit to the next, so you have to monitor your usage constantly - takes forever...