While I am sure that the DD-15 is, indeed, more than up to just about any job, I would just add that the DD-12 that I have in my system is also quite the overachiever. My room is not huge, but it does have significant bass-suck issues, and the DD-12 corrected all of those for me, and is barely coasting along (compared to its capabilities).
Either would be a good choice, I'll wager.
Either would be a good choice, I'll wager.