I am biamping my MG 3.5s with a Marchand 126s (Balanced I/O) active x-over. I am using ARC VT100 MKII for the treble/midrange and Kenwood L07 monoblocks for the bass panels. The results are incredible. Careful selection of output levels and x-over points and slope are required for seamless blending. In order to faclitate blending of the amps, I used a 6dB/octave @ 250 Hz slope for the high pass, whereas for the low pass I used a steeper slope, 18 dB/octave at 200Hz. In general, I would recommend a gradual slope for the high pass section and a steeper slope for the low pass (assuming that the solid state amp is driving the bass of your speaker).
