Ross, if you are wanting loud bass that is still tight, then what you are wanting is referred to as a "single reflex" box. I have used these in the past and you can make a 10 sound like a 12 and whatnot. The downside to this is that the box is nothing short of massive. Essentially you are having to build both a vented box and a ported box for the same speaker. The speaker fires into a sealed box while the backside of the speaker sits in the vented box. I used to run a pair of Orion 10" DVC's in a single reflex box. That was great. But, each speaker required a cubic foot for the associated box and that was running the speakers at their bare minimum sizes. A 12" speaker would need a box that is about 2.5 cubic feet for each speaker, or something about the size of the area behind your rear seats.
If you need any help building a speaker box, let me know. Another one of the things that I have invested some time into.