Scan 18w/8542 in 2005 Escalade doors..Sealed or not?

I have a 2005 Escalade (like Tahoe/Yukon size) . the doors seem to have a lot of interior room inside. I could use polymer clay by Cernit and enclose the space or I could just run IB.

I am not sure if I will use the Scan speak 18w/8542 as a midwoofer or just as a midbass driver. Either way...it's what I have to use right now.



http://www.scan-speak.dk/datasheet/pdf/18w-8542-00.pdf

So sealed or IB? Not SPL at all just pure SQ.

I would cross at 80Hz to the sub.