Louder 12 inch subwoofer than Rockford Fosgate Power HX2 (daily driver)?

[kevin G]

I am thinking about buying a new 12" subwoofer. I have a Rockford Fosgate Power Series HX2 tied 1 ohm to a T10001bd (birth sheet said ~1500w at 1ohm) currently. I am thinking about getting a FI BTL but what else would be louder? I want to upgrade not go down.

Also, price is not an option, and I am probably going to buy a new amp too. When I get a new car (within the next year) I'd rather upgrade at that time instead of finding out later I missed an oppurtunity, otherwise i will just transfer my current setup to the new car.