This is awesome

The JL W7 line is one of the best subwoofer lines available. They are slightly on the pricey side but if you want the best you have to pay for it. I am running a 10W7 from a 500/1 and focal utopia components off a 450/4 with focal polyglass coaxials for rear fill. I use the 10 inch purely because it is rated at 500 RMS and I have no need for any more bass, I have become too accustomed to the use of my ears! The W7 is an awesome piece of engineering and I have listened to the 13.5, 12 and 10 and could not find fault with any of them in terms of SPL or sound quality. The only problem I could mention would be that installation is not the easiest thing in the world but a product of this quality and price should always be installed by a trained professional. I find it hard to believe that fredfunktified, who reviewed the 12W7, works for JL as he claims. I have listened to the 13.5W6 and used to run two 12w3d4. There are extremely good subs but attempting to compare 2 or even 3 W3's to using a W7 is ridiculous, you will never get the same quality and how much boot space do you want to take up. If you have the money buy the W7, if you can't afford that buy the W6 and if you can't afford that buy the W3. It's not brain surgery. Where possible you should always listen to a product before handing over any cash but you won't be dissappointed by the W7. For a full technical review of the 10W7 check out http://caraudiomag.com/testreports/0210cae_jla/.
If you are bored by all of the technical stuff just scroll down to the bottom of the page to the listening review. If you don't trust me maybe you'll trust the best car audio reviewers in the business.