Sven the Sexman 
Why isn't the EQ off?
Set gain properly, bass boost off, infrasonic to the point where your sub will reach Xmax at your maximum nominal power.
Derp.
How big was the old box?
This is what your new box looks like before cabin gain:
Heres probably what your old one looked like based on the JL rec specs:
Apply some filters to emulate a 50 Hz LPF and cabin gain, ignore the low SPL on these graphs, this particular program wasn't designed to do this.
Vented box will make more "boom boom" above 25 Hz, but the sealed does better below that. Even more so if you factor in the vented box unloads around there and would require a SSF/HPF to prevent you from hitting Xmech.
Vented clearly producing more sound in the "useable" region.
