I just picked up a King Kooker double burner propane stove - brewed with it for the first time on Saturday - it's perfect. Each burner is 54,000 BTU, and it's solidly built - brought my wort to a boil quickly.
Amazon.com: King Kooker CS29 30-Inch Two-Burner Outdoor Cook Stove: Patio, Lawn &...