Yes you should but there is no need to get something with that high of wattage for a 55 gallon tank. If you have taken all the info on this thread and covered 3/4 of the top and placed the hot spot closer to the basking area you will achieve 115F with a 50 watt bulb and it will keep the ambients at range. Just dont use those diamond halogens for the reasons already stated. Just tinker with the lighting and basking area until you get the needed temps. You do that by elevating/lowering the basking spot.
A.