As I have said before go with a installer who has done the training and fits them regularly for extra warranty , throughly clean the system, change all the rad valves at the very least , fit a good quality mag filter and new controls should have a trouble free system but should you be Unlucky at least the backup is in place, 100 is midrange good quality boiler , the 200 is the top of the range with weather compensation bit over above your budget that is me done now . (Baxi is still a the affordable way to go bud )