I'm pretty sure that the common agreement on the L7's is that they are supposed to be ported.
I was really looking into buying one about a month or so back, so I read up on them quite a bit. A guy I talk to has a pair of Kicker L7's ported. He says the SQ is great.
I've heard that the L7 not only is louder in ported boxes, but sounds better.
Note: I'm just telling you about the research I have done, not actual experiments.