The Flatline and OZ subs are pretty deep....they would be difficult to get into a box with 1.0 ft^3 internal volume.
Arc 12D4: Built for Arc by Imagie Dynamics. Very transparent, plays low, blends very well, needs about 1.2cubes
Also consider Dayton, Alumapro MX, Boston Pro (they make a single 2 ohm VC)