can you not output XLR from the Preamp into the power amp
and at the same time output from the RCA outs on the Preamp into the first subwoofer and then chain that to the other sub.
Once the setup above is done, use the crossover, phase, and level controls on your JL Audio F112v2 subwoofers to integrate them with your main speakers.
The F112v2 also features the D.A.R.O. system, which you should definitely use with the included microphone to optimize the subwoofers’ response in your room. @sdavada
you can verify this with JL Audio though