If you're looking for subs that love sealed enclosures and get pretty loud, I'd recommened Infinity Kappa Perfects (Not the DVQ, but if you can afford the DVQ then by all means go for it)cant go ported, these subs will be under a back seat of a truck so very limited on getting exact space for sealed.
My two perfect 12"s in a sealed 1.8gross cubic ft box were pretty **** loud. Ask kcdc30, he heard em.