I want to rig up a subwoofer, but I know that crossovers are expensive,
and since I am running high powered commercial amps, I'd need a hefty
setup. Then comes the need to combine the left and right channels
without loosing stereo separation.

I decided to go another route, My power amp was 600W (RMS). stereo. I
got a good deal on another amp that is also a stereo commercial amp,
rated at 500W RMS. Both amps are bridgable. The plan is to run the
outputs from my preamp into Y adaptors and feed the left and right
channels to BOTH amps. One of these amps I'll bridge and use that to
power a single subwoofer speaker.

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?

I have also thought about just putting an equalizer into the input of
the amp that feeds the subwoofer and raise the low end of the frequency
and cut the highs. I'm not sure if that will adaquately work or not.
I'll probably try it, but I have not yet built my subwoofer cabinet.

Either way, I know that 1100 watts rms is more than enough for a home
stereo...