yep it is, not tried it myself, but have downloaded some video clips on a usb and it worked, so dont see why the harddrive wont work,
if you dont want to go trough the remote control route than you will need some more adaptors, not looked into it too much but its alot more cost, but saying that the link you gave with the dvd plyer before, shows that it works using the rnse? not too sure so cant really say, using the goolge translation it does control some of the dvd players, not sure if it controls the one his selling, best to ask the seller,if it does control than its a bargin i think, cause you get the multi media adaptor and a dvd player