The easiest way to set gains is to turn your h/u volume between 1/2 and 3/4, slowly turn your gain up, listen to your woofers, when they start to distort or sound like they have reached there peak, back off just a hair.
Right now ive got them in a sealed box and they slam pretty hard. But if u put them in a ported box they could put out some pretty decent numbers for the price. I plan on getting a ported box one day, not sure when that will be tho. I would definately recommend them if u wont good spl for a not so expensive price.