I am sure there is something in the pro world for running powered speakers that would work. Maybe call sweet water and ask them.
Some active crossovers will let you run 3 subs with active gain output (preamp). Sublime acoustics is a good example. Two subs could run off the RCA outs and one off the XLR as both are active at the same time.
For background music I would just use a Y adaptor or two and turn up the receivers sub gain 90% and then adjust it down in the subs as needed.