Id look into digital designs 2500, 3500 or 9500 series woofers over any Fi subs. Depending on your desired power level. If you're wanting to run one woofer Id do 600-800 rms to a 2500 series, 1000-1500 rms to a 3500 series, and 2000-3000 rms to a 9500 series
DDs have far better coil cooling in my experiences so you're able to play the woofer full out for longer without having to worry about reliability issues. The 3500 and 9500s both have a much much stronger motor than the W7 and will embarrass it for SPL and street beating.
For pure sound quality obviously the JL has the advantage but hardly anyone goes for pure SQ...most people want a good daily driving woofer that can play a variety of music loudly and reliably...not a competition level SQ woofer. The untrained ear of your average Joe would never fully hear the difference in SQ between a decent sound quality woofer and an elite level sound quality woofer anyway.
Also another point is you're going to want a sub that is reconeable. DD, Fi, T3, Kicker (solo X only), Audioque, DC and many others fit the bill. Usually most recones are in the $100-150 range plus labour and you have yourself a brand new woofer.
The other option Id look into is DC Audio. Theyre a new company based out of Nevada. Great sound quality, and get super loud. They've currently running 4 different lines of subwoofers.....300 rms, 600 rms, 1000 rms and around 1500 rms. Check them out at
http://www.dcsoundlab.com/home.html
Id also not waste your time with that overpriced JL amp....theres nothing at all special about that amp despite the hilarious claims I hear from salesman. And the amp is only stable down to 1.5 ohm which is almost useless for a class D not to run down to 1 ohm. You should be able to find the same power from another company for half the price or under. Or preferrably spend the same amount of money and get 3 or 4 times the power.