One without a GUI. The CPU and Ram will be too slow for a decent GUI.
The hdd is no problem. A web server with a CLI will use 300-700mb. Neither is the vid card.
If you intend to run MySQL you need 256mb minimum or you will get strange errors.
See tutorial here for a command line debian based system:
http://www.daniweb.com/forums/thread78131.html If i am helpful, please give me reputation points.