if you're gonna use it mostly for HT ... you don't need the DD-12 (believe me)
there are other ways of finding a good location for your sub: Room EQ Wizard software, SPL meter, and your PC is a great start. (very cheap too)
personally, I'd go for the SVS plus/2 + Velodyne SMS-1 (only because I'm too lazy to learn the Behringer Feedback Destroyer as EQ) ... this combo will boom the DD-12 out of your house. [remember this is for HT usage]
I also have a 2600 cu.ft. room. The velodyne DLS-5000R is already way too much, it gives craploads of SPL - something 90% of the people look for.
The other 10% of the people read these forums and then want lower frequency extension (upgradeitis is contagious btw ... it is internet borne). but you're not gonna get your money's worth. you have to pay a lot more to get a little more. again, value is relative to your budget and how infected you are with upgradeitis.
since your budget is around 1300 and you want to get maximum benefit for your money. I would recommend the SVS plus/2 which coincidentally is 1299 bucks. (oh, and so I wouldn't be accused of being an SVS adboy, check out HSU research also).