I would still recommend
NAS4Free or
FreeNAS (in that order) over Amahi, but that is solely based on their stated capabilities as they relate to what *I* want them to do (i.e., my primary goal is for long-term preservation of all my data). There is also a 4th one to consider which is
OpenMediaVault. All four packages support NAS functionality, all are free to use, all support use as a media library, and all are based off some flavor or Linux. Amahi is based on
Fedora at this time, but it looks like they may be moving to
Ubuntu (which is based on
Debian) in the future. Both FreeNAS and NAS4Free are based on
FreeBSD, and OMV is based directly on Debian. All of these OSes are widely used and very stable and well-supported, but you may want to make sure that
all your hardware is 100% supported by checking the hardware compatibility pages for each respective OS. You're using an off-the-shelf server, so the hardware Dell used
is most likely widespread enough that it will be supported, but there are times when e.g. your RAID or wireless card won't work (lookin' at you, Debian!). Granted, your server probably won't have a wireless card, so that's less of an issue.
Anyway, take a look over the feature pages for the server software, and decide what all you want the box to do.
Amahi
FreeNAS
NAS4Free
OpenMediaVault
There are many, many more Open Source NAS options out there (e.g.
Rockstor,
openfiler, and more) but the above four seem to be regarded as the easiest ones for non-techies to set up.
ONE VERY IMPORTANT THING regarding your NAS storage pool: One of the things the Synology and QNAP boxes manage for you that can be a pain in the ass with the roll-your-own server model is adding disks to expand the size of your storage pool. If you're planning to add more drives to your server later to grow its storage, make sure you research the process
NOW to see whether it's something you'll be comfortable doing later. FreeNAS' and NAS4Free's reliance on the ZFS file system, for instance, means you can't just tell the storage pool to be larger by including the new disk, you have to copy your data elsewhere, add your new drive, reset the NAS pool to the new size, and then copy the data back...which can be a pain.
--Patrick