I have an SB-1000 and a used to have an LFM-1 EX. An SB-1000 can't begin to keep up with an LFM-1 EX and doesn't have the low end extension. I definitely would not pair an LFM-1 with and SB-1000, and you should stick to larger ported subs.
For another sub to consider in that price range, also look at the RBH I-12. Or for a little more, the Rythmik LV12R.