Rick:
We have Hope V4 "downhill" brakes on our touring tandem with a Shimano IceTech 203 mm rotor in front and a Hope vented 203 mm rotor in the rear. They are for a flat bar setup, but Hope makes disk calipers that work with both Shimano and SRAM master cylinders for drop bars. The V4 brakes will bring the tandem to a halt better than any rim brake solo bike I have ever ridden. I also have them on my fat bike where they are overkill, but they were available this winter when Hope "enduro" E4 calipers were not.
I also don't have to deal with glazed over brake pads or squawking brakes. Loaded with riders, gear, and the bike, the whole thing weighs about 450 pounds. I doubt that you weigh more than 400 pounds. Have all the disk brake bikes you tried used cable actuated brakes?