I guess the NAS adventure requires a why you need this? Let's see, I can recycle old computers I would have had to stash or trash. I wouldn't have to buy a huge honking hard drive for my own use that only I can use on my PC. (I don't need that much disc space, personally.) You see with a NAS on your network, everyone on your network can get at the files stored on it. Why is that important. If you gots family, multiple PCs in the house, and you are each downloading videos off of YouTube or NetFlix. A NAS is a central storage place everyone can access. Let me paint a picture.
"Anybody download the movie for tonight? Yeah dad, but Jimmy's got it on his PC and he's out on a road trip. (Should have burned a disc or put it on the NAS with the big honking hard drive.) I'll download it, burn it, when I'm done watching you all can have it."
Download it once directly to your NAS, it is there for anybody on your network. Lots of redundant effort foiled. It is practical for storing any digital documents and media. For me this means I have a huge honking hard drive that my various small PCs can use and not have multiple versions of the same docs floating around on each PC. It also means that my many CD library can be stored away (real backup copies) and disc swapping is a thing of the past.
This is busting the description of the home PC. A PC must have a keyboard and monitor and used by one person at a time, thus personal. A PC is only good when it can do everything the person using it wants. NO! You can dedicate a PC for certain uses. Like managing a entertainment system. A TV tuner card, media software, stereo speakers and home theater r us is yours. Connect to your NAS via your network and that huge honking hard drive(s) is a well of assorted entertainment. You can watch it on your big screen or your laptop.
If you are concerned about the noise level of old computers, buy new power supplies and cpu fans, have a techie install them. The newer stuff is quieter. But the point is that computers can be configured to share and not be so.......personal.
A NAS is not NASA, that is not rocket science, but does require technical tenacity (getting your geek on) or getting a geek professional or buying a commercial NAS unit $$! Home brewing a NAS just sounds like fun and useful. I'll let you know.