Currently I'm running with a pretty big sealed enclosure.
It's a "wedge" enclosure (as says on the box wizard). 39.5" wide, 20" tall, 24" deep (bottom) and 12" deep (top). It has insulation on the inside as well. I didn't build the box, but the person who did left an opening between the chambers.

If I would stay with the sealed enclosure, is that opening good, or would it be better without?

Really, I want a loud but somewhat clean bass. It gets pretty loud right now, but I know if it'd be ported, it'd be a lot better.

The two 15s (4ohm DVC) are powered by an Audiobahn A1500HCX amp. They're wired down to 1 ohm atm.