I have a Kicker 700.5 powering a ported R. Fosgate box with two punch 10" subs. I get a weird occasional vibration from the speakers when I turn things up. Some songs sound great, some songs get the vibration, like a rattle from the sub itself. I tried hooking an Elemental Designs 11ov2 to it for comparison, same thing.... maybe a little more pronounced. I have the bass boost all the way down, the gain at about the half mark, and lo-pass set at around 90-100 Hz. Any thoughts? Using the factory head unit...