over heating the amp?

Check to ensure that you have a good ground with a low ground return impedence. If it is a high return impedence, this too can lead to many an amplifier heating up very fast. After the amp shuts off, feel the heatsink. If it is hotter that a sheet metal roof on a hot day, there is a major problem, either with the ground, the load (bad sub) or the amp itself. If the amp is shutting down and is not hot, then I would look closer at the subs. Hook one sub up at a time and retest the system. If one sub caused a shut down and not the other, then you need to look at that sub and the speaker wire to the sub from the amp. Top Secret, I can tell you but then my wife will kill me.