That's why I was suggesting the SB2000 as well. 625 from their outlet is a good deal and comes with a full warranty. I don't think you'd feel like you didn't make the right choice with it and it's not too far out of budget. In your room I think 1 would sound great, and if you upgrade in the future get another. Worst case scenario you send it back, no harm no foul.
The VTF -3 MK5 is a whole 'nother animal. You'll get the most bang for your buck there. It's tunable and you can run it ported or sealed. I'm 90% music and do critically listen. They're great sounding subs. I set my speakers to small and crossover at 80HZ after running room correction and it's the best sounding system I've owned. I don't regret buying them at all, but I had a bigger budget.
Decision, desicions...