Go to Decware.com, enter the site, click the speakers tab and there they all are.  There is a nice write up for each and a link to the plans.  This should answer most of your questions about sensitivity figures and stuff.

Both the DB and WO can be used with 12's with no info for 15's.  Check the forums further for info on these in oversized boxes with larger drivers.  There are designs specifically for 15's, like the Housewrecker.  People put those in cars too but any of these designs scaled for a 15 won't fit in a car.  Van maybe, but the HWK for 15's would make a van a 2 seater.

Adrian, it's a little horn.  It's a whole lot louder than ported.  I have proof.

[quote author=bassboy  link=1152142581/0#3 date=1152194420]Adrian, it's a little horn.  It's a whole lot louder than ported.  I have proof. [/quote]
my reply was based only on what i've read. it was a 12" version.
things may vary from car to home, but anyway, i would choose wo over ported.

Have to go with the WO on being louder than the DB with a given wattage and driver