I've got a some vintage Korg and Novation rack synths that I route through a rack-mounted stereo line mixer. From there, an 8-channel snake runs over to my mixing desk that controls all my outboard sound gear and connects to my DAW.
My modular is inserted on a stereo pair between the rack mixer and the desk mixer.
To make that work, I needed balanced stereo ins/outs, so I went with a Vermona TAI-4. Shortly after I got it, I discovered that overdriving those transformers adds such creamy distortion to those vintage synths, that I fell in love with that Vermona module. Glad I spent the money.
This is my current modular setup. In the future, I'll be adding several more filters, reverb/chorus, and more modulation options.