In article ,
wrote:

However, I need a means to send only the bass to the amp that powers the
Subwoofer. Is there any sort of crossover made that goes in the input of
the power amps, after the preamp?

Sure. http://www.marchandelec.com/xovers.html for one.

I use an XM9 in my own speaker system. Each side has a
midrange/tweeter/midrange array with a passive crossover, powered by
one amplifier, and a side-mounted subwoofer powered by a second
amplifier. The XM9 divides the signal, after the preamp and before
the amplifiers, crossing over at 200 Hz.

http://www.radagast.org/~dplatt/speakers/

20+ years since I build it, and I'm still thoroughly satisfied with
the results.