Before buying equipment and stuff hit me up that way I can help ya on getting what you really want. I think you'd like the deal I can hook you up on and once you hear what I have installed your mind might change.
If you want your bass to be loud and have a good frequency range a custom ported is needed. For one 12 a custom box will not run you a huge amount depending on how fancy you go. Investing in proper wiring, a quality amp and a custom box will make a huge difference.
If I ended up going pre-fab on my first sub, would I have to go with a sealed for it not to sound bad?