I have a Snail shell. It produces really really low booms. The thing about the snail shell, is that it's HUGE.. 33x13.5x18 over 3cubic feet. but it produces great boom. If you go ported, you can get a customized round ported or slot port for the price of a snail shell.

If you go 2x12 Targas...you can say goodby to trunk space hehe. Each sub requires 2.5cubic feet at least!..for ported. So 2 would be at least 5cubic feet. But if you do go 2 12" Targas, you'd be spending most of your money on a good amp to power both..though a V12 1507 or Thunder Audio 4100 will do..if you're on an SPL budget like me hehehe. Then if you rear fire it...you're going to need sound deadening since you're going to get heavy trunk rattle which is very disturbing. I suggest try auditioning 1x12 Targa in a snail or ported. 1 12" Targa is pretty good na, and will make you grin.

Here's a pic of my trunk showing the gap between the box itself and the rear.


And here's my box front firing..I do front since it minimizes my trunk rattle by 90%. As you can see, my trunk space is already gone with 3+cuft occupies