I actually just bought a display cabinet from IKEA of all places.
What sold me on it was the adjustable shelving.
http://www.ikea.com/au/en/catalog/products/40116876
I'll probably add a mirror to the back, and lots of extra shelves

This one was nicer (and slightly larger), but didn't come in black:
http://www.ikea.com/au/en/catalog/products/10115562