There are IB specific subs. Fi Car Audio has a line of IB3 Series and Exodus Audio has the DLP-10 and DLP-15. Links to both sites are at the top of the page and the WinISD files for all of them can be found here:
http://www.hometheatershack.com/forums/diy-subwoofers/14410-downloadable-winisd-pro-files.html
http://www.hometheatershack.com/forums/diy-subwoofers/14410-downloadable-winisd-pro-files.html