Which ones..
 

Looking for opinions here.
What do you guys think would sound better? A single RF P3 15, or 2 Kicker Comp 15's?
I will have them in my back seat, being pushed by a 1900 watt amp. (Which I highly doubt actually pushes 1900, so)

in my opinion kickers dont sound great but get real loud

do you mean on your back seat? if so i have yet to hear one on the back seat sound good

Yes, On the back seat.
I had 2 12's sitting on my back seat while they were waiting to be sold, since it was easier to remove if somebody wanted them. But they sounded pretty good still in the back seat. And the part I like more about that, was there was barely any rattles outside, as opposed to when they were in the trunk, it sounded like the car was going to fall apart from the outside.

Your thread shows tells me you must have a lot of background in this topic. Can you direct me to other articles about this? I will recommend this article to my friends as well. Thanks

either subs will work, it will all depend on the box when it comes to the performance of the bass.