For those who want similar overall performance to the 18.0 for significantly less money, we also have our 18.1, it has a db or 2 more output 16-25hz, a db or so little less 30-60hz, and roughly equal above 60hz. The only drawbacks is that being a ported design it has no useful output below ~15hz, and it is a little larger, and not as nice looking.
Also there is our 18.0C that offers overall about half the output of the 18.0 under 60hz(they are actually near equal above that), for about half the money(FYI we do offer discounts on pairs), so for nearly the same cost you can get roughly the same overall performance split in two. However even though it is smaller than the 18.0 two of them do add up to a larger overall space.
Then there is the 18.3 that for only slightly more cost than the 18.0 gives you ~6db more output 13~30hz(in the lowest tuning mode, in the highest tuning mode it offers up to 9db more output than the 18.0, at 20-25hz, at the loss of output under 18hz).
Also all things considered raw output is not always the end game when considering what you get for your money, what all our subwoofers are primarily designed to excel at is low distortion(specifically the more objectionable high order distortion(s), that are especially noticeable in the upper range of a subwoofers use. This facilitates better and easier integration with high end speakers), high upper range efficiency, and low compression, which in combination with solid output capability offer the best sound quality and dynamics possible, at often more than satisfying output levels.
