underpowering a sub will definately wear it down slightly but that is depending on the brands (i.e. jensen 500 watt amps are very different from JL 500 watt amps). I would say what you have is fine (depending on brand) just dont try to push a W7 with a 100 watt amp
companies also sandbag, some exagerate, so if you're really worried about it it is best to test your amps output
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Pioneer Premier, Elemental Designs, SoundSplinter, Resonant Engineering Audio, Stinger, Optima, Rockford Fosgate