Not all jumpers are cheap POS's. Mine are big and strong enough to tear a nasty hole in someone. Not that I have any experience with that.

My car speakers have the ability to be bi-amped. They have two inputs and have a switch for a single input or bi-amp/bi-wiring. I doubt they would spend all that time and money putting it in for nothing. That's what led me to think the passive crossovers might do something different with 2 signals entering vs 1. I haven't tested out how effective it is though. It just doesn't seem very wise to say they don't do anything without actually testing it. Those without a switch may have some sort of automatic detection built in. I don't know.