No offense, but I find it almost impossible to believe MTX rates their speakers at half the power they can actually handle. That would be 'underrating' their speakers on a scale never seen before, by any manufacturer that Im aware of. Remember, hooking a certain sized amplifier up does not, in any way, guarantee its producing rated output (either due to system voltage, gain settings, etc). Im not trying to question your enthusiasm for MTX products, but imo suggesting that MTX subs, virtually all of them no less, are underrated by half, is only going to lead to blown subwoofers by people who believe you.
Its true many people place emphasis on 'underrated' products, as if it is a sign of quality (which it is not). But many people also look at rms specs of speakers as a sign of quality and/or output potential (which is not really true either), and to underrate whole speaker lines by half would be a pretty stupid thing to do in terms of marketing.