I think I am getting closer now, and want to run this by you all.

If I put one of these L-pads on each of the 8-ohm horns, to lower the volume level to match the 16 ohm horns. Are these at Parts Express good ones?
Eminence PX-LPAD Crossover L-Pad Attenuator | Parts-Express.com

I would run the 2 pairs of horns out of the Pioneer with AB speaker outputs.

What about this xover, with 6 outputs.
BBE DS26 2-Input 6-Output Loudspeaker Management System | Parts-Express.com
It would appear to a novice like me that the 6 outputs would be right and left on 3 different channels.
One set of outputs would go to one power amp and then to one pair of woofers, one set to the other power amp and then to the other woofers, and the last set to the Pioneer and the 4 horns, with the 8 ohm horns having the L-pads attached to the speaker in between the input wires and the horn wires. Is this right, or is this crossover overkill for a stereo? I have read some bad things about the Behringers quality, and I would think it would be simplier to have just one box with the 6 outputs that I need instead of 3.

What about resistors that were mentioned? Any recommendations on exactly what I need? Also, I have read that I need to know the frequency response of each speaker to set the xover. Does anyone know where I can get that, or it is just a matter of playing around with it tell it sounds the best?

Then all I would need is the XLR to RCA jacks, so I can plug everything together since all my amps have RCA plugs? Am I missing something, or does someone have a better place to buy or like a different brand?