The Solo X has a 45 or 55 depending on who you ask, either way no ferrite has been tested above it. Too bad Kicker put a terrible set of soft parts on it. The 10s and 12s were great with a much weaker motor. The 18 could have been king had they done proper soft parts that didn't weigh 14.5lbs(exaggeration).
Anyways, I'll stop derailing.
Skar, looks like you finally have a product that is competitive in the range of woofer many enthusiasts are looking for.