[mikegett]

It is the SW7324. I don't know off hand what the volume recommended was, but the RMS is the same as the SW7124. 450 RMS per sub. Underpowering could easily be your issue. The quickest way to tell, is turn your volume down to a moderate level. The bass should sound cleaner. If you believe so, then download a sine from caraudio.com or elitecaraudio.com. It can be found in the subwoofer or amp tutorials. Look for a 60htz sine wave. Place the sine wave on a cd. Your going to try and find out where your amp is clipping at. Clipping can be hard to identify on your subs so be patient. Place the cd in your HU and unhook your front speakers if possible. The 60 htz sine wave can do some serious damage to your speakers and overheat your amp in less than a minute. So be very carefull. Play the wave in your HU with any bass options on and at your normal setting. If you use bass boost or keep the sub at full volume then place those settings there. Raise the volume till your hear the sine wave distort. I strongly suggest being as close to the sub as possible only run the wave at thirty second intervals to avoid overheating the amp. I am going to guess that you will hear the wave distort at one quarter volume. If you have the gains maxed already, then it may distort at 1/8 volume. If this occurs, then you have a choice. You can lower your gains so that the amp will not clip till you have the HU increased to a higher volume. We can get into that later. I would still like for you to describe the sound of the subs. Used, they could be blown or not sealed properly.