Recommendations needed for indirect water heater

In 2011 I installed a propane fired Triangle Tube Solo 110, to feed the radiant floors and panel radiators I installed in my 2600 sq ft house. The plan has been to migrate to an indirect tank once my electric tank started to fail. That's now happening.
I've considered the Smart 40, thought there are some indications that the Smart series have had issues with leaks, and have also seen good feedback about the Turbomax product. Water here is drawn from a well, and is mildly acid and moderately hard before it's filtered, pH buffered and softened. Ph is right around 7 (checked monthly by me), and there's probably a little extra sodium chloride from the brine back washed softener. 2 full time occupants, 1-2 overnight guests on occasion. 1 energy star dishwasher, 1 high efficiency front load clothes washer, 1 1/2 baths: main bath has (2) 2.5 gpm shower heads. I plan to set up a re-circulation system on the indirect, as well...Thanks for any and all advice, your recommendations are appreciated.