Bad subs, or amp?

I had a problem with my system about 2 months ago and everything went nuts, the subs started slamming uncontrolably and I got loud engine noise. I took every thing apart and thought I found the problem but no it turns out it was caused by the sub amp and it ruined the head unit, so I got a new headunit thinking that was the cause and hooked everything up and thats how I found it was the sub amp that did it. I'll get a new headunit tomorrow, but how do I know its the amp or the subs causing the problem without ruining another headunit? The subs are Kicker 15" L7's, and the amp is a Mark Anthony 3000D.and the headunit is a Pioneer DEHP7800mp. Any help would be great, I need it!!

How is the amp hooked up to the head unit? High level or RCA?

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Looks like a wiring problem such as a short somewhere.
When you test next time, disconnect the line feeds between head unit, amp and sub's amps. Just give them power. Nothing should happen.

Then test them backwards, one thing at a time, which will also not destroy your HU if that was the case. Start with your sub. Upon connecting the signal RCAs from the amp to the sub, nothing should happen. No circuit protections coming on or any noises. If all is well so far. Instead of using your HU as a test machine, you can also use an old CD player's outout to connect to your amp. YOur system should play music thats on the CD (or Ipod etc).   IF all is well so far, you can connect your HU and that should work as well.

First of all use something like a multimeter and check to make sure you arent shorting anything anywhere.

It would hurt to have to lose a HU this way!