Dear Brainwater: Awesome systems you own, both the 2 channel set up and the HT.
As you know JL Audio has an excellent reputation on the Car Audio subwoofers area. The Gotham is their top of the line HT sub design ( not for a true stereo set up ), I never herad it so I don't have any opinion about, you can directly contact with Carl Kennedy at: Phone: (954) 443-1100 .
Btw, I can " see " that the subs in your 2 channel set up are a passive one design. I wonder if you would thing in the integration, on a true stereo way, of active subs instead your passive ones?. The self-powered subs has many advantages over the passive ones, one of those advantages is that the sub amplifier is designed excatly to match with the characteristics of the drivers ( woofers ): damping factor, frecuency response, very low THD, output impedance, etc.... I think that no one universal amplifier can approach the " dedicated sub amplifier design " quality sound reproduction through the subwoofers.
Regards and enjoy the music.
Raul.