So, I've rigged my 2-way crossover for the passive side, biamping it using the EC AW75. Biamping is a good option, perhaps enough for many. Clearly worth it to my ears ! Easier to deal with, for sure. Before starting this I thought there were more options for crossovers, but I can't find many 4-way at all. Did a measured approach, combining pink noise and sweeps, and got a result I feel is pretty good. My levels for each driver was ok by ear, but some form of EQ is needed when including the room. The two speakers don't match exactly, as expected with this crossover. Hard to tell by listening. I'm both impressed and pleased . There's a better clarity to the lower octaves, better tonal distinction. Have to make a rear cover and connector plate, 2x speakon perhaps...