hi,
I have also contradictory echoes from the JBL forum in France. An "authority" of the site, to my big suprise, advised me the same: keep the passive part and pug the crowns with the 1kHz crossover point respected... An other one, adivised numerical crossover like the one you said, or DCX 2496, they all do that it seems.
I will have a look at the passive crossover upgrade (audiokarma thread, I think) as Grumpy said. I went to fast on that one....
An old repair guy here told me the same: bi amp is lots of trouble for an uncertain result....
BUT on the other hand every one gone bi amping is not wanting to come back to mono.... and there is that:
http://sound.westhost.com/bi-amp.htm
I think i will give it a go. I will just buy one crown and if it sounds bad I will find another use for it (Home cinema for instance). I will give it a try on one speaker running in mono (not stereo) and keep the passive part on the mid and high. I will let you know....