To be honest, you're going down a rabbit hole with this one. I've been doing media servers and client pcs for last 9 years. Currently, I'm running a server with 2x2TB and two client PCs that wake it up when they come on.
Recommend you spend a lot of time in the Home-Theater PC section of the forum, read as much as you can.
Quick solution: Buy an out-of-the box PC with plenty of capability/expansion for harddrives, running Windows 7. Make sure it's 5.1/7/1 surround sound, support 1080i/p HDMI. Then, spend a lot of time ripping your DVDs/Music to it. After, BACK IT UP!!!! Preferably to an off-site harddrive.
I've had my music, DVDs, home-videos, and pics on my server, can't imagine going back to the manual method.