I would like to replace a 14 year old Rheem gas water heater with a new indirect DHW using my existing Burnham Series 2 boiler (80.2% efficient according to the sticker). I have had 4 professionals look at the system. 2 would just add a third circulator to the exisiting header and new pipe as needed and two want to totally re-pipe the boiler. The reasons they state were the same.
1. The existing header is only 1" and I need a 1 1/4" to support the two heat zones plus DHW.
2. The current circulators are connected to the boiler return and pulling the water, when it is better and more efficient to push the water
3. Except for the boiler, all other devices around it (air scoop, check valves, circulators, etc.) appear to be 20+ years old and I should replace it all now to avoid piecemeal repairs over the next 10 years

I already upgraded the boiler control to a Honeywell Aquatrol AQ25142B with outdoor reset and DHW priority.

Based on the information above, is it worth twice the cost to replace everything around the boiler now?

I also couldn't find much about which Indirect DWH are best. I like the Vaughn/Burhnam stone lined, but one plumber told me they are not good for the type of water we have on Long Island and reccomended Techtanium or Superstor.