The Kickers are the way to go here- they move more air because naturally a 15 inch square has more area than a 15 inch circle- thus more air moved =greater spl =LOUDER. The only thing that might get some equality between the two is if the db drive round sub has a far greater xmax that is the linear movement of the cone from start to full excursion-IF the db drive has drastically larger xmax than it could possibly outperform the L7 because of greater cone excursion which also =more air moved=louder---- haha thats a tricky one but ya got me wondering too so let me know what you find out please-Ive always been a kicker fanatic so im probably biased towards their products-never heard nothing bad about db drive though either im in salt lake city i dont know of anywhere out here that even carries their products so i have nothing to reference by except kicker L7's kick asssssssssss