A NAS is a certain commitment move. Do you get a PC of somekind and convert it, or do you go with a device and the inherent limitations of a dedicated device (capacity limit due to architecture, non-upgradeable memory, constraint to a single interface, etc.). I have strugged with this for at least a year as I have reviewed various options. In the end, a device seems to be the answer for me.
I have decided upon an iOmega ix2-200 because it plays nicely with Linux and I have some hope that when 2TB drives come down in price, I might be able to plug them into this. In the least, the drives are changeable so if there is a device failure, I can replace a drive. That is a pro over something like a WD World Book where the drive is built in — it fails, you buy a new unit altogether.
I do not need my NAS to be on all the time, so that helped guide my decision. The key thing that drove me to a NAS is that I want this accessible from any computer (physical or VM). I have been trying to work with a secondary PC with drives hanging off it, but it lacks the compact nature I am really looking for — even with ponderances of boosting the internal storage.
I am looking forward to getting into this so I can have an archive of my material. Given what I am going to use this for, I believe I will keep it in the RAID-1 configuration so the data is mirrored. The entire device would need to fail to make the data inaccessible.
Here are a couple of links for edification.