This is my media server I put together from various parts left over from my old LGA1366 gaming build, and a few things I found laying around. So a lot of this will not make sense for a new media server :)
CPU - Yeah I know, 'an i7 in a file/media server?' Overkill, but its doing the job. I left it at stock speed and undervolted it to 1.0125V to lower the power/heat. Cooled with a Hyper 212+ with a fan from a Corsair H100i
RAM - Also underclocked and undervolted for same reason. The LGA1366 platform defaults to 1066MHz so I left it at that and lowered to 1.4V.
Storage - Found an old Seagate HDD at work that I slapped in just to run Windows. The main storage is a mix of WD Green and Red drives which total 11TB with 3TB reserved for parity data, so 8TB usable. Plenty of space for now, but if I add more, I plan to go with 3TB Reds.
PSU - Just looked for an affordable good quality PSU with enough SATA connectors. This fit the bill.
Instead of a true RAID5 solution, I'm running a free little program called DisParity. There are a few reasons I went with it over RAID and it was very simple and just what I wanted. The main benefits I liked are 1) all disks don't have to be the same size, and 2) its easy to add disks to the array at any time.
Hopefully this build lasts for years to come!