When I looked at coil interaction I found that it was quite easy to alter the mH rating by altering the distance and relationship between coils. If you have a spare coil and an LCR meter it is easy to see the changes happening in real time.

I would also add that reducing the DCR of coils will have as much, if not more, impact on the crossover than the ESR of newer caps - I would urge caution in this area.