I have a masonry fireplace that is large enough to accommodate most any insert that is offered. It is 36" wide/ 24" high/ 24" deep and 27" wide in the back of the fireplace. I am looking for a insert that performs as stated in the title. I do not mind if it is catalytic or not. Does anyone have any recommendations for a insert that does have ultra low emission's, high BTU output, and long burn times.