which is the best data storage device ?
that depends on what you would like to do with the storage device.
First of all, it should have at lease 2 drives(mirror), also check which harddrives are supported, check the cpu(the slower the worser the performance) and offcourse get gigabit network.
i myselve owbn an icybox(will not advice that) and a small homenas from sitecom. This lastone performs very will and its about 50 euro's(without drives).