We have the 2013 Montana also. When we ordered the unit they said we
could not get the heat strip or heat pump. So we went with the Fire Place which works very well and is much quieter. It heats the unit
on chilly nights and mornings. We really don't miss the heat strip
or heat pump at all. If you can add a Fire Place in place of a cabinet that might not be a bad idea. Usually there is a cabinet in or around the living room area that you had the option to add the optional Fire Place. The Fire Place has a 1500W heater built in. Or just go with the 1500W heater as others have said. Hope that this helps.