I would go for the ULS, the performance for the money is enormous.
Here is my recent review of it. I would say you are looking at two to three times the output of the SB2000, if
these numbers are correct. By the way, I part company with speakerman where he ways the S1500 is more musical. The ULS-15 smokes the S1500, and yes, I have heard them both. I think speakerman was using it in a configuration that emphasizes deep bass, but the ULS can be adjusted to put more weight on mid bass, if so desired, and this will place more emphasis on traditional music instrument frequencies. I would be willing to bet that the ULS could keep with PSA's sealed 18", the S1800 without much of a problem.