do a search. there was a comparison of the jl w7, idmax, and diamond d9, and a couple others if i remember. the difference in spl was so close. all in all they are very similar in sound and spl. if they are the same price go w7, if not id's are a bit cheaper new and authorized. either way you cabn go wrong, and i would shy away from 1000rms on the id max. they dont seem to like it that much. more like a 800rms woofer. can take 1000 in a small sealed box though. the id's will drop lower with more authority than the w7 from my experiance with both woofers, given a decent install.