I have had multiple power series amps and have never had one problem.If you have had and installed multiple amps and they all had issues what they have in common is you.
How much a sub is moving does not necessarily determine how high it's output will be, actually at box tuning the excursion should be the least and the output the highest.
If you are trying to compare everything to the havoc and seeing if you can find something comparable that should give you the answer right there.
Why search around for something comparable when what you want is readily available?