Rules - my concern is to thoroughly investigate the parameters and then compensate as necessary. I will develop the Thiele-Small parameters of the old and new drivers to judge how the changes interact with the crossover. Furthermore, since first-order crossovers utilize the midrange over a very broad range, the exact placement and shape of the response anomalies are important. The new crossover must match the response profile of the new driver.
All that said, Rob has been shopping for a drop-in replacement and this driver has been recommended to him by knowledgeable sources. Power disparity would matter - 30 watts raises questions, but the 10F is our best present solution. My job is to subject it to further scrutiny.