Heater question for 55 gallon?

[vaindioux]

Hi

I just got done cycling a 55 ga tank, it is all ready to add fish. I had a brand new Hydor theo 200 watt heater that just failed, it cooks the water at 84 degrees no matter what I set it on.
Since I need a replacement shall I get 2X100 watt heaters or only 1X200 watt? i will get a different brand of course.

Thanks a lot

Patrick