I have exactly the same problem with my 12" MTX sub, although RAP sounds OKish, but when I put some trance or house (which I listen most of the time) it sounds just too terrible...gain is turned down almost to nothing, but I still can get clean bass. I have just talked to my friend, he said that it happens because your deck does not devide audio signal into separate frequency, i.e Hi, Mid, Low and thus it feeds all of them into sub. I have 1200 w amp and even having gain turned down to nothing, I cant get what I need. What he suggested to do was to install a couple of crossovers to divide the signal, however, Im not sure and need someones expert opinion on that one.