I think the server idea is cool, even though its a LOT more money, I would do it if I had that many dvds and the money.
But I second the Sony DVD changer idea. I've messed around with one at work and they seem to work pretty well. The changer will read and identify all of the dvds. You can program the dvds by categories, action,drama,etc. and easily search through the discs by either remote or keyboard(you can attach one to store and recall). Everything is on-screen and since most DVDs support jacket pics, you can see the dvd covers as you're searching for the DVD. Definatly a more economical way to store the discs.