hello, i have an mtx 801d which is a decent amp and a respectable company. i bought if off ebay. now for the problem i accidentally hooked the ground and pos. opposite. anyways im not sure if this would cause the problem having seeing that the fuses did blow thank god. unfortunately im not sure if it worked when i got it. but anyways well my subs work cause i tested em out with a home receiver. however in my car they hit really randomly HARD like every 3-6 seconds a real quick hit and its terrible maybe its "bottoming out" cause like i can here coils or something in between its weird. i have to completely take off the face plate to. but do u think its the amp or could it be something else or maybe even the sony h.u.? maybe a bad ground ? apreciate any opinions