I hear you Doc but it's nice to send the lows as in this fellows case to the sub and run the main speakers above the xover freq. thus using the main amp with more efficiency due to the fact it does not have to reproduce the lows. I have not seen amplified subs that will accept low level input that output via low level just above the xover freq.to the mains. It's quite nice to have the control of the filter on the main speaker amp. Been there done that. Having said that it's just one old mans position on the matter. Perhaps an idea for BH to produce an active line level xover as proposed for your Jagers. Peace out, no hostility intended.