Solar heat to boiler conversion.

Charles, just seeing how you made out. If your plan is to have the amtrol as a back up, you need to leave your boiler on, which is not what you want, I believe?. Hopefully you piped the system with the solar tank feeding the amtrol and installed a bypass to be able to operate the solar tank only. It is only then that you can turn off the power to the boiler and isolate the amtrol.
 There is one other way you can minimize using the boiler while still having it available for backup. Keeping the tanks in series, you add an aquastat control or high limit control to the pipe exiting the amtrol. Wire this control to the power of the boiler. Then when the temperature get below a certain set point, say 100 or so, it turns on the power to the boiler and it makes hot water as designed.
 So hopefully throughout most of the year, until you need heat, the solar tank will be hot enough to keep both tanks at a warm enough temperature and the boiler off.