Best Active Crossovers?

What are the best active crossovers?

I have a pair of Dunlavy SC-VI, which are four-way 6db slope crossover.

I understand I would need to use Three Krell KBX in series to get 4-way 6db slope (besides 8 channels of amplification).

Do you know of any high quality 4-way active crossover that can be configured to 6db slope (except for the 3x KBX option)?

Thanks!