Does anybody make...

I'm not sure how this DIY project works without an active crossover.  Marchand is the right call.  Their X-overs can adjust gain into each channel and pass.  

OP - You have all of your answers above, pick one and start working. You have a limited time on earth.

@fiesta75 

Thank you for your contribution and I will take it too heart!😊

https://www.decware.com/newsite/ULTRA.html

Steve Deckert explains all the different ways to use this preamp, just read past the first page… it’s on my shortlist.