I think the 15" HF driver would do quite well in that situation. It may not get quite as loud as the Titanic but it may be a bit more musical. It is designed to be their "High Fidelity" driver
The only thing I can suggest to do is to try it out. I believe though that it modeled better in a 2.0ft^3 enclosure. I can check it again though.
If you are after serious low end (flat response below 25-30hz) without an eq in the system, ported is your best bet.