Bill, if you rent an active subwoofer (power amp built in and crossover), you only need to provide and output from your console, CR, Aux from each keyboard out, even perhaps voice too, that way, you donīt have to get a crossover, amp, etc.
I use also an active subwoofer all the time and sounds GREAT !. There are some like Mackie, HRS150 Active Subwoofer, Mackie SWA1501 , Yamaha MSR800W, the new Roland KCW1 Powered Subwoofer (200 Watts), here there are different models, power so, depending on your needs, ANY will work beautiful, hope it helps.
------------------
mdorantes
_________________________
mdorantes