I am running a JL 13.5 with a JL XD 600/1. I will tell you that my setup is MORE than required. I have the Dirac system in the M5 which is OUT of the world with the JL setup.
I would however have to agree with other fellow members who say that the factory Logic 7 is more than sufficient.
I do switch off the music, roll down my windows half way and hear my V10 with catless headers and RPI full exhaust. That exhaust note is what I paid all the money for
I later thought of getting into a 8 inch sub but then just gave up on making changes. My setup is all stealth, you cant tell where the amp is, you cant tell with the sub woofer is and thats what I Love about it.
The reason I ran a sub is when I did the CIC, I felt like I lost a lot of bass and that made hunt for a sub woofer setup.
The good part is, the amp basically has no weight and I can always remove the sub and keep it in my garage if I need too.