I was always using active Xover, but do know what you mean about passives.
For a boxed wide ranger I agree about keeping the Xover out of it. On OB you run the risk of running out of XMAX pretty quick on a wide range driver trying to reproduce bass.
Yes, very true! I changed out the input caps on my amp to a smaller value, so the amp itself doesn't produce bass below 100hz. Protects the midrange driver and is way better sounding than a big coil and cap in the signal path.
I've been active in the past with a miniDSP 4x10HD. But I moved away from it in part because it bottlenecked everything to 24/96 and I have a lot of DSD recordings. If I ever go back to fully active, I might check out the First Watt B4 which is from Nelson Pass.