I agree on AudioControl but not on the RTA part. If you know frequencies very well and you know what kind of sound you are shooting for, using studio or high quality monitors as a reference, then I always say that the ear is the best instrument. And plus I don't want a ruler flat response in my car, I want a response that is going to emphasize the good qualities of the interior while diminishing the bad. Flat in a car is not a good thing because the amplitude response of those midrange frequencies are a killer. I can't stand hearing a car system where the mids are tuned flat to the interior. Sounds like ass. But the flattening in the other ranges is a very good thing, especially in the upper low range (150-500). Who knows if this guy knows his frequencies, probably not, but I am just saying I trust me ears more than any machine.