the 9500 can have some decent sq as well as great spl. i've heard a couple of single 12" installs, and they on average sound great. the only one that didn't was spl all the way. tuned 50hz, and if i remember was hitting higher 140's(that 's on a a/c.) with around 1500 rms. i am not a car audio specialist, but i know what sounds good to me, and the 9500 fit the bill. not the most accurate thing by far, but is a very good sub to do both. l7 imho is just loud providing very little sq wise. but i've only heard 5 intalls, 1 was spl oriented, and the others tuned reasonable.(30-35hz). still had a hard time keeping up with much besides rap.