a house of your size with a apartment will be pretty
demanding on a heater...
I would go with a 75 gallon Rheem Fury or PRO unit
you might be able to squeak by with a 50 , but that would iffey......
I dont know what is available in colorado as far as models
With a recirulaiton line installed , it might be wise to
put that pump on a timer.... if you are worried about economy
as far as thickness of insualtion, you can always
add a blanket on the heater for 15 bucks