The absolute best place to purchase an enclosure for that sub is to take the specs to a person who designs and builds boxes. Don't buy a pre-fab... it will choke the output unless it's designed absolutely for that sub.
Edit: Oh yeah... Don't go bandpass unless you've got an HB, grocery getter, soccer-mom box on wheels, or exploder wanab. The bandpass box will only hinder the output in comparison to ported.