With the W7's SGLC (short gap long coil) design- it would naturally appear to be more SPL warrented. However, in this case, this design increases the speakers BL linearity and reduces distortion- thus making it suitable for SQ purposes.
Personally, I have found that the w7's claims are a bit over-exaggerated. Frequency response is limited by the massive surround that reduces cone area, as well as the general motor structure in general. Slight breakup and distortion is present at lower frequencies and midbass respose also suffers on the other side of things. JL did design a very good subwoofer, however, there are still room for improvements. IMO- the w7's are sonically no different than the w3's and hold little advantage over them.
The price that the W7's boast is by far way too much-any way you look at it.
Go with the W3's, and enjoy! They are some fantastic subwoofers and should give you several hours of listening bliss.
take it easy,
-zane