0.4 ohm is pretty high limiting DF to 20.
Here is an example of good inductor for the woofer:
http://www.parts-express.com/14-gauge-c-core-toroidal-inductors.cfm
Here is an example of good inductor for the woofer:
http://www.parts-express.com/14-gauge-c-core-toroidal-inductors.cfm