bi-amp sub?

In the interest of dispelling myths: the reason you need the amplifier gains set exactly the same and the input signals to be exactly the same is to avoid magnetic field cancellations in the voice coil assembly that can reduce your output.  The woofer will not be physically damaged by opposing forces generated by different signals (unless the power input exceeds the ability of the voice coils to dissipate the heat.)  The opposing forces will simply cause loss of voice coil motion.  Two equal signals 180 degrees apart will simply cause the voice coil to stop moving.  If you are at or near the power limit of the coils, this loss of motion can cause them to burn up much faster than normally since it is the motion that cools them (as well as what generates the sound waves.)

So, bottom line is the woofer will not be "torn apart" or any other catastrophic disaster like I've read before here and elsewhere, but it can cause poor performance and faster death by heat.

Actually the only "catastrophic disaster" that can occur is if the coils burn up.  That's all that can happen.  Different amounts of power mean nothing.  It's different phase that causes loss of output and excess heat.