For music only I think Sonos to stream music cant be beat for ease of use, will play all the music off your hard drive plus all the streaming Internet options. It creates its own wireless network.
Vortex box appliance from Small Green Computer is a ready made media server
Small Green Computer. They do have a 4tb model that would handle your 100 DVDs.
I think a lot of people use a Mac Mini as a easy to use media server using the Apple Tv and iTunes as interface.
For myself I just bought a Soundscience Music Vault. Very robust and ready to use out of the box. Can stream wirelessly over my Sonos but also has digital out to play lossless files fed into my processor and amp. Also as a server you can log in from anywhere.
Music Vault II