It could be adequate. I'm not sure how loud you like to listen, but you did say you need to fill your basement with sound. It could be that a Hsu VTF-3 or VTF-15H would suffice. PSA also offers a 15" sub that's less than a grand. That's why I say chat with Tom Vodhanel on the PSA website, let him know your situation, and see what he recommends. Two twelves are fine for me, but my room is less than 2500ft³. Your basement will take a lot more effort to pressurize.
Or you could consider a DIY project to save some dough.
This sort of build, for example, using
this Dayton 18" HO driver plus a
$200 Crown amp and a
balanced/unbalanced converter would put the i12 to shame. (See the attachment on the first post of
this thread for the build plans.)
Edit: Or the
Stereo Integrity HST18 or the
Mach 5 UXL-18 in the
Stonehenge flat pack is another interesting combo, and ought to be easier to build since all the box parts are precut. I've not modeled either of those drivers in that enclosure, so I'm not sure whether either is as well tuned as the Dayton combo linked above. If I come across any informative build threads I'll link them.
Would a DIY project be worth considering? Would you be more likely to consider a flat pack solution than something built from scratch from plans and sheets of MDF or birch, even if it means spending a little more?
Thanks for fixing the negative karma, by the way.