I've got 2 10" Kick Comp C10 4 OHM DVC, I was thinking about ditching them for some 12's, but then I figure why not just get one more and run them at a 2.67 OHM load. Would they sound better/louder than 2 12's?
Unless you want the most dB's you can get for your $$$
Take your entire budget and invest it in one good woofer, you use less space (generally), weighs less,less power(or in most cases, better power at the same price).
Of course there are several other things you need to provide, im not so sure the Kickers are the best for your application.
Im all for the 1 woofer idea. I ran 1 12" in my 01 GT and was More than happy with the output. I ran 1 12" RE SX powered by a eD NINe.1 amp. Ported enlosure 2.25@33hz