I just bought a 15" fi btl dual 2 ohm off of craigslist.  The box that came with it is obviously way too small and tuned to high.  I was wondering if anyone could help me figure out what size of box and all that stuff I need to get what I want out of it.   The current box is 19"x18x17" that's about 3 cubes and inside that enclosure is half port and the speaker.  Way too small.  It lacks lower end very much. Im running it off of a autotek ss1500 at 1 ohm. I want it to be audibly loud and hit as hard as possible.  I have built many boxes but just want to really make sure this one comes out really well.  Any suggestions would be appreciated.  Thanks.