I got a Western Digital My Cloud 8TB NAS thing for I think about $400. Here's the link on Amazon:
http://www.amazon.com/WD-Cloud-EX2-...932&sr=8-10&keywords=western+digital+my+cloud
So far so good with it. You login through a browser to manage things. It also has external USB ports so you can attach other drives to the network. HOWEVER be aware that it's 4TB of usable space because it has mirrored drives. I lost a 2TB drive full of stuff after accidentally knocking it over. Thus my reasoning for a setup with RAID. I'm pretty sure you can turn RAID off, but I wouldn't recommend it. If you spent $400-$500 on this thing, you probably didn't do it for zero redundancy.
I've been redownloading my movies and TV shows I bought plus re-ripping the most important ones to put on this drive. So far it works pretty well. It's also set up to use for a Time Machine backup, so I've been doing that with my MBA because remembering to plug in a portable HDD was not easy. As soon as I get some things sorted out, I plan on moving another external drive to this setup so I can get the TM backups off the mirrored disks. I don't need a redundancy of a backup.
I'm trying to get it to work as a storage location for my Photos library. I had some copying issues that I think were unrelated to the drive, so I just created a new library on the drive since most of my photos are on a TM backup from an iMac. I may have accidentally killed my iMac, thus I'm going through this. The only trouble right now is getting the shared folders to stay connected. I think this has to do with IP addresses, but I thought I'd share this little trouble.
Really it's pretty good for the price I paid. I really wanted the RAID mirroring and it came setup for that out of the box. I had to do a couple of Google searches to figure out some initial setup, but my only problems since have been keeping it connected. Reconnecting is almost always just going to it in Finder again, but it's kind of a pain.