If you've got the coin then go with the level 5's. They should be substantially louder than 1 level 3 15. You'll need a stout electrical system though because with that setup you'll want to start pushing some serious power. Also, you considered the XL's?
well really i used to have two kicker comp 15s, and i want something that is gonna be way louder than that but with the best cost so your guys opions would be greatly apreshated, if i can get louder with the level three, im gonna go ahead and buy the right amp and drop some good money into a box, but if not im gonna sell it and save for something thats going to blow it out of the water, so what do you guys think??