I will run the crossover in the 12/6/1 as it was intended. The 12 sub i plan on wiring one jack to the crossover, and the other jack wired for no crossover for when it is used with the active crossover in the BX1500
I would encourage you to get the cross over section ment for the 12sub, and the cross over with switchable mids for the 12/6/1. That way you will have the mid content balance, and your woofers will be crossed over at the same frequency with the same slope. It will eliminate a lot of issues.
From what I understand, running your cabs the way you describe would send the lows to the sub, and the mids/highs to the 12/6. Which would render the woofer in the 12/6 redundant, and give you the same volume as running your single 12/6 on its own.
Build em with the greenboy specced cross overs, and bridge your BX1500 and run them mono.
