I have a 32gb microSD card that I am using for additional space.
I have music and movies on it and they run fine (using MXplayer plus codecs)
You can also fit a SD card onto the dock as well as USB hard drives(i think)
Yes USB hard drives formatted as FAT32 work great for music and movie storage/playback plugged into the dock's USB ports.
Sent from my SPH-P100