I had a pair of SB1000's for a while. They're very smooth and clean subs, but won't do it in a medium to large sized room. If I had it to do again I'd go ported. Well, I did go ported, but my room is huge and so are my new subs!
Have you looked into any other brands? You might get a little more bang for your buck with
Hsu or
RSL. There are a couple more, but I'm not remembering right now... Don't be too quick to discount that Speedwoofer because it's only 10". It
reviewed very well here and by all accounts it punches above its weight class.
I like that you're going with duals too. I wouldn't go with just one any more.