I would checkout the DIY section and download Winisd and play around with the parameters for various woofers.
I would actually work the other way and tell you to determine what size subwoofer you can fit in your home. Along with that we need to know how large your room is, and your budget. Those three factors can help determine if you should go ported or sealed. 12", 15" woofer, or 18" woofer. Some drivers can model pretty well in both ported and sealed modes, but if you can't fit a big ported box in your room, sealed might be the best way to go.
Hope this helps.