No, the Dayton F model is not lower in sensitivity than the Vifa that you have in there now, it is actually about the same, but the impedance is a much closer match to the original D26 series "Hales" vifa, so it will cross properly and hopefully get rid of the peak that you are dealing with.
If not the photo's that I have of the Hales crossover show it being fairly simple, I would just need to know how you would want it to change and need a shot of both sides of the board. as long as you can do the work, you will end up with a great blend.
