I'd leave the drives and replace every cap and resistor in the crossover. I wouldn't be surprised if there are complete crossover replacements available.
The JBL Everest and the TAD 4001 are top tier products. However the TAD4001 is not a direct replacement for the driver in the Everest. At least without a careful crossover change and measurement. This would be a project for an advanced hobbyist.
You must have a verified phone number and physical address in order to post in the Audiogon Forums. Please return to Audiogon.com and complete this step. If you have any questions please contact Support.