What about Diamond D3 8s? Ive got a pair of Dual 2 ohm D3 8s in a pair of .9 cubic foot boxes tuned to 32hz and they get real low and pretty loud for 8s. Im running 250 watts into each one. They are not as loud as my single D3 12 in a 2cuf 27 hz box, but they are not far from it.
I got mine...