So, two systems have been proposed by two installers. Similar but slightly different. What I'm basically interested in is the tank-in-tank Triangle Tube Smart 40. Is this type of indirect superior to the coil types? Also, any opinions on Veissmann Vitodens 100 vs Munchkin 80 mod/con boilers?

Anybody?

tank in tanks are excellent tanks. The viessmann is a great boiler. the munchkin 80 is a fine boiler in the hands of a good installer.