While there is nothing wrong with Synology or QNAP, if you're the least bit capable of building and/or managing your own hardware, do some research and consider going with a FreeNAS box. I struggled with consumer grade NAS products for a couple of years, none of which were that great as far as my expectations. I looked into FreeNAS, and after building a fairly inexpensive PC to run it on with six 2GB hard drives, I've never looked back. It sits next to my desk and runs flawlessly, providing Time Machine volumes for my Mac Pro, Mac Mini and two MacBook Airs. I also run Plex on it as a media server.
I will say that I run the "old" version of FreeNAS (9.x) rather than the current version. Nothing wrong with the current version, I'm just happy with the older version and more comfortable working with it.
Just something to consider if you're "handy". Setup and configuration is really simple, and there's a very broad and accomplished user community out there that does a great job supporting it.
MacDann