Other sub amp for Gallo Ref3 secondary voice coil?

Hi - any Gallo Ref 3 users out there driving the secondary voice coil with a solid state amplifier other than the Gallo sub amp? The manual says you can use any 100WPC + amplifier that is stable into 4 ohms as long as a crossover (60 Hz or lower) is used.

I am driving my Gallos with tubes (with great results), and I don't have a "sub out" on my integrated. I was thinking about using a Rotel RB-1080 (200 WPC) to drive the secondary coil, and putting a crossover on the interconnect (like one of those little FMOD units). Just wondering whether someone had tried something similar...