Heat, most homes with hydronic heating are planned out by the builder to have enough radiation in the baseboard, hot air ducts or true radiant in floor to heat the building at 180 degree water within the heat loops, if you are able to heat yours with 160 degree water then enough radiation was installed to do so, most homes are not! Higher heat loss at higher water temps are going to always be a factor BUT with the newer high efficiency gassers, stack temps at the breach of the boiler are a huge factor, measuring that stack temp tells a great deal about the stove.
Example, I have measured my old WoodDoctor when it is running hard, at times it will reach a stack temp of over 1200 degrees with flames coming out of it's stack!
Last February I ran a HeatMaster G 200 ( severely undersized for my load ) we ran the snot out of that poor little boiler in order to keep up with my load, I monitored the stack temps on it and never once saw it exceed 450 degrees.
Both boilers were set at 180 off and 160 on!
Have you ever measured your stack temps?