do like i did and start by looking at the thiele perimeters of subs and compare to what might fit your needs.that will take alot of guess work out if you do some research and watch youtube vids for sound pressure levels.me,i like my d6.unfortunately,it cant hold the wattage im looking for and only the fi bl loaded spec's is the only driver that has similar thiele perimeters so i have to go with that cause thats the sound i want.if you have had a sub before and can find the T/s perimeters of it.then use that as a basic tool for your sound needs.you have some homework to do lol.