My advise is to build a large porter enclosure. It will be hard for one sub to full that space, and I am afraid that if you build it sealed, you won't have enough power from that wimpy amplifier to get any decent performance as sealed enclosures require a lot of power. Plus being that you are only building one for such a largish room, the ported sub will beat the sealed sub by approx 8db throughout the low end.
So with that being said, I recommend plotting those drivers in a ported enclosure in winISD to figure out the best enclosure size and port tune. That amp is not very powerful, so I would highly recommend saving up for a new one sometime soon! You might be able to get somewhat decent spl initially but adding a new amp, like a Behringer EP4000 or iNuke 3000 would make a good difference!
I don't have access to winISD at the moment due to being on my iPhone 5 and no access to a laptop, but I am sure that someone like LTD02 would be willing to help you with the design!