Replace Navien with an IBC SL at a 60% surcharge over an older, proven IBC DC?

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I have a Navien CR240A thankless and KD-HBO100 heating box installed 10 years ago. The unit heats domestic water for two people, as well as heating a basement floor, an area that is also heated by a furnace. We run the shower, washing machine, and kitchen tap for minutes to get hot water. There are two pin leaks in the heating box which are not reparable because of the small diameter of the piping. The CR240A has failed numerous times with expensive service calls and delays waiting for parts from California. Now doing my own maintenance, my inventory of spare parts has proved useful.
A contractor had recommended a Bradford White Combi tank, but has since deemed them unreliable. He now recommends an IBC SL14-115-G3 boiler with a stainless indirect tank, or an IBC DC33-160 combi boiler. The SL14 is the latest technology with a ss boiler, a remote digital control interface, limited lifetime heat exchanger warranty, and a 60 Gal ss tank. The older design DC has two independent copper coils in a cast aluminum vertical fin heat exchanger, has a mode that pre-starts the boiler based on past demand, and a 10 year limited exchanger warranty. They have similar AFUE numbers (95%), turndown rations, and basic warranties. The SL14 costs 60% more than the DC33. Adding a recirculating line to the DC would reduce the surcharge to 52%.
1) The SL14 provides 14-115 K Btu/h, while the DC33 is 33-160 K Btu/h. Given that modulating-condensing boilers are more efficient with minimal cycling, wouldn't the DC20-125 be closer in size to the SL14, and preferred with its lower 20-126 K Btu/h range versus the DC33?.
2) Go for the DC20 (or DC33), and add the re-circulation line if DW delivery delays are bothersome?
3) Warranties for both units require annual inspections by a certified technician, ~225 Cdn$ each year. Are there ways to reduce this cost by making my own observations, flushing the unit, etc.?
4) We installed a Calmat water treatment system a couple of years ago to address the hardness of our tap water. Is this adequate for the IBC units, or should it be replaced with a different technology?
I look forward to your valued input. Thank you.