I've read that changing to the JBL 075 driver from the 275 would be an improvement. N-800-D XO's already in place bypassing the N-600's.
Other than the N-800-D XO's, this unit has had no other changes and looks and sounds like it is new (maybe a little dry from the surrounds age but none the less in excellent condition).

Anyone made this modification and was it worth the effort from an acoustic point of view?