I have a pair of Vandersteen 2Ci speakers that have a blown tweeter. It is a 6 ohm VIFA D19AD-05. It is not available any more. I would like to replace it with a new VIFA tweeter that is a 4 OHM speaker. I would, of course, replace both of them at the same time. How, if any, would that affect the crossover. The speakers are being driven by an amp that can handle the 4 ohm load. What would have to be changed in doing so.