well, if it's for the 24 gallon JBJ, it might be too much because if the hood is close enough to the water level, and you don't have any decent fans, the lights will warm that tank up higher than you want in no time. But, like I said before, I'm not familiar with those systems. All I know is that with my nano wave, I had to cut extra vent holes in the hood, AND put on a fan to curb the heat. And then I had my heater on a timer to only come in at night. I'd wait on getting it though till someone with experience with the JBJ chimes in.
Just to let you know though, my total tank volume is 26 gallons, and I have no problem with the 50W. Remember, your pumps will also give off some heat....not a lot, but it might be the difference between having a 50W and a 100W