If you want a sub for spl, id get the audioque hdc3. Has the potential to get way louder than the 15" kicker l7 and its about the same price as the l7 too.
DD Audio makes great SPL drivers. I have modeled many of these and noted a peak resonance in nearly every enclosure that had to be compensated for SQ. So, most of their models are spl based that I have noticed. mainly the higher end models. Just a thought.