Biamp question

I'd be careful with and active crossover that doesn't fail safe. A Behringer DCX2496 will fail to work but not send the wrong signal to the wrong place. I only use an active XO in my Bass management system. I find there is a lot better protection with a passive XO for mids and high. 300 hz and below I'm direct coupled too. No passive crossover. I don't recommend it, out of the gate though.. Hook up your amps and be happy. Quit making it complicated.. You want to mess around later, you always can.

Regards

If the output of the Parasound is louder than the Rouge then you are good. But if the Rouge plays louder, turning the Parasound down won’t work.

I’ve bi-amped with two of the SAME amp, but slightly different minor versions, and felt even that sounded a bit disjointed. So I’d be surprised if a high power SS amp and a high power tube amp meshed well. That said, the Rogue tube amp sounds much more akin to SS amps than you might expect for tubes. And the A21’s gain control is certainly an asset for gain matching the two amps. IF you find the Rogue’s gain to be higher than the A21+ at its max level, you can drop the Rogue down a few dB’s by subbing 12ay7 in the V1 / phase inverter slots in place of the 12ax7’s. It works well; I've tried this. I like the red-label GE 12ay7 from 1962 or 1964, I think (very specific year on the red labels) :)

A 5751 sub its also good for a dB or 2 and sounds nice on its own merits (if you have a good triple mica black plates vintage).

I'm doing exactly what you trying to do. I use a Parasound 21 for the woofers and a tube amp (set 300B's) for the tweeter and midrange. I looked at your preamp outputs. I run my Parasound with XLR outputs from streamer/Dac directly to the Parasound and  RCA outputs from streamer to my set amp. My streamer /Dac does not have an output selector so both outputs work at the same time. You will have to figure out if outputs from your preamp can be run simultaneously. Otherwise you will need a splitter. The gain from the XLR out will be twice what the RCA output is, so if your stuck using a splitter use XLR. Also, you are correct as the gain control on the Parasound can be used to set the woofer volume to match the tube amp output. I use a program called REW and microphone to adjust the output/volume levels on the Parasound to match the tube amp volume. But that's another "rabbit hole" No messing with the crossovers-Parasound to woofers and tubes to tweeter/midrange speaker posts. Sounds sweet. 

@backdoor 

"Thank you all! I believe I can manage the active crossover (possibly) but my chief concern is disabling the crossover in my speakers."

As it should be.  The crossovers do much more than dividing the frequencies.  They also may include-

1) Baffle step compensation (reduces front baffle reflected midrange and treble so as to even those frequencies with the bass, can be as much as 6db. 

2) Impedance flattening circuit.  Makes the woofers easier to drive and have a flatter response curve.

3) Notch / peak suppression filter.  Reduces the magnitude of driver break up frequencies or other frequency peaks that a typical crossover and slope cannot deal with. 

avanti1960 - I don't agree with the benefits you've listed, not even one. Nothing is going to give you a flatter impedance or response curve than eliminating those capacitors and inductors. Together with variable crossover points and or a DSP, you will accomplish everything you have mentioned much better and greatly reduce intermodulation distortion. I know you won't agree, but that's what this forum is about, sharing opinions and knowledge. Happy listening, no disrespect intended.