Car Stereos: Amplifer or Subwoofer, sony head unit, sony xplod


Question
So a few months back i decided to add some bass to my car.  I bought a 1200watt Sony Xplod sub woofer, a 1200watt xplod amp (looking to wire a second sub when i could afford it) and a sony head unit as well.  

recently i experienced some problems where the sub would not hit like it was supposed to, it barely made any sound at all.  It sounded like a crackling noise and i was under the impression i blew out the speaker.  Days later i purchased a brand new sony xplod speaker (identical) and hooked it up, once again the sound worked for a few moments maybe an hour or two before the brand new sub did the same as the first.  I unhooked everything and reinstalled it about a week later and the same process repeated.

I don't believe its the speaker because it will hit and it is brand new, the connection and wiring should be fine but i'm not ready to rule that out yet.  i do believe the problem is in the amp, maybe i blew out the amp and its not sending the signal to the subs right, when i asked for advice from people more educated in car audio than myself they believe it sounded like somethings wrong with the amp too.

hopefully you can help diagnose the problem and let me know how to fix it.  I looked up the amp warranty policy on sony xplod and it said signal and connection problems are not covered, does this also mean if the problem is the signal from the amp to my speakers i cant do anything about it?  I was hoping i wouldn't have to replace anymore of this system that wasn't covered under warranty

thanks for your help

Answer
Brian,
I am little confused on what happens.  Before I give you my answer, I would like to get it straight.  If you unhook it all, then rehook it all back up, does it work for awhile, then stop working?  Does it ever start working without rehooking it up?  What is the model number of the amp and the model number of the subs?  Whatever the outcome, you shouldn't have to replace anymore components.  Let me know, and I will give you a specific answer.  -Scott