I don't know how the damage was done, but it's not uncommon for a DC pulse from an amp to take out a woofer without affecting the tweeter. With any luck, you should be fine with a fresh driver.
If you want an upgrade from the 8545, consider the new Purifi 6.5" driver. It has very similar specs, but sounds much better at twice the price. I've made that substitution in a Merlin VSM speaker without modifying the crossover.
If you want an upgrade from the 8545, consider the new Purifi 6.5" driver. It has very similar specs, but sounds much better at twice the price. I've made that substitution in a Merlin VSM speaker without modifying the crossover.