A ported box built to the specs of the sub will NOT be *boomy*. It's only *boomy* if the specs of the sub and the box don't match........... or the sub is a real piece of crap OR the sub is old and the suspension is gone.
If you want to get really loud, definitely go ported. But buy a sub that likes to go in a ported box...........
Current : 2013 Mini Countryman JCW
Past: '88 E30 M3, '69 BMW 2002 Ti, 2000 328i, Audi A6 TT, BMW X5 3.0i , Audi A4, Mini Cooper Clubman S 1.8T