I have used products from Buffalo, Netgear, and some no-name network attached storage for my home network and they all pretty much work poorly.  The big drawback to those devices are the network port, cpu, and the software that is installed on them (OS).  While most devices these days advertise a 1,000 MB/s (Gigabit) network interface they never achieve that rate or even come close to that.  With all the of the previously mentioned devices, I could download files from my internet connection quicker than from my local network device.

Enter the HP Micro Server.  This device has a real processor and room for 4 2TB hard drives (someone mentioned that you can up that to 3TB but I have not verified that yet).  Since this is a real server you can expand the RAM in the device and the network interface actually works at 1 Gigabit. 

There is no operating system on the device, so you are not paying for an OS you do not want or need.  Install Windows, Linux, or FreeNAS on the device and you are up and running.  You can even use an SSD or USB thumb drive to boot the OS which makes the device rock solid.  Below is a link to the HP Micro Server on Amazon.