You will not.go wrong with Big Maxx. I have one, what size and what fuel? Or electric? If fuel(ng or propane) you will need to purchase venting. When I bought mine it came with propane burner. At same time I bought the orifice for NG. Only about $30 to have both orifice.
Natural gas found output formula square footage x 60 wich puts me at 57,600 so I'll go with the 80000 which is output and Menards has it on sale for $400
