@almarg - You are totally correct. I didn't even think about the miniDSP. In addition to the input impedance issue, all the miniDSP devices will convert the analog input to digital before doing the crossover processing - then converting back to analog. These conversion steps as well as the very poor power supply section of the miniDSP will just kill any sound quality benefit you would be getting from the Modwright preamp or audio source. You would do better to look for an analog-only crossover. There are a couple of Bryston 10B crossovers for sale on Audiogon. They have input impedance of 15k ohms, much better than miniDSP. Also, completely analog and much superior power supply.
That being said, I did think of one more thing. You should consider any built-in passive crossover inside your speaker. Are you using a manufactured speaker? Or something you built yourself (DIY). The internal crossovers of the speaker will conflict with any active crossover. While you could potentially set the active crossover above/below the internal crossover points, you are just wasting a step. If you do have internal crossovers in your speakers, you are just better off using a Y-splitter cable to go to two separate amps and take the active crossover out of the system completely. On a 2-way speaker, you could potentially just bypass any crossover wiring internally and wire directly to the speakers. If it is a 3-way (or higher), this becomes more complicated because you'll need to have some sort of internal speaker crossover to separate between mid/tweeter. The internal crossover will have this, but it will also have a high-pass section to rolloff the woofer frequencies.
If you can't control this and it's a manufactured speaker, an idea would be to connect the Modwright amp to the mid/high binding posts and not use an active crossover for this at all. For the woofer, you could use an active crossover to the Crown amp, but then wire the crown amp directly to the woofer (do not use the internal woofer crossover). All this will require some DIY work on the speaker to accomplish.
Let me know if I haven't explained these ideas correctly.
