My first suggestion would be titanium. If you don't want to go that route, I'd check out the Rena Smartheaters... just got one for my 33 gallon and it's nice, it alerts you with LED lights if your tank is too hot or cold, and also when the heater is heating. You can also plumb it to a canister. Pretty cool. Fluval makes those other heaters that do similar stuff, but they are just glass heaters with a case over them, unlike the renas.
Someone is going to suggest ebo jager, but im not a fan.